Inappropriate antibiotic consumption promotes antibiotic resistance. However, findings on the association between antibiotic-related knowledge and behaviors are inconsistent and contradictory, resulting in unjustified guidance of interventions. The mechanisms between the different kinds of antibiotic-related skills contained in knowledge modules in some previous studies are indistinct and rarely studied.A cross-sectional survey was conducted between June 2017 and April 2018 in three Chinese provinces, investigating 9526 parents with children aged 0–13 years old. Data from 1944 parents who self-medicated their children and 2478 respondents whose children sought care were analyzed.Skills for antibiotic identification were found to be a moderator for the association between skills for antibiotic use and two inappropriate behaviors. Compared with parents with low levels of both skills for antibiotic identification and use, those mastering both skills at either medium  or high  level were less likely to self-medicate their children with antibiotics. Parents with a medium level of skills for antibiotic identification and high level of skills for antibiotic use  and those with a high level of both skills  were less likely to ask doctors for antibiotics when seeking care.Parents’ high level of skills for antibiotic identification is revealed to promote inappropriate antibiotic use when parents master a low level of skills for antibiotic use. Conversely, based on excellent skills for antibiotic use, better skill for antibiotic identification is associated with a greater reduction in inappropriate behaviors. We recommend future health education to strengthen skills for antibiotic identification along with guidance on antibiotic use.The online version contains supplementary material available at 10.1186/s12889-023-15099-8. Antimicrobial resistance (AMR) has been identified as one of the top ten global health threats by the World Health Organization (WHO) in 2019 . InapproA considerable body of research has studied the relationship between knowledge and behaviors of inappropriate antibiotic use , but witAmong the antibiotic-related skills, skills for antibiotic identification have sometimes been neglected. Antibiotics have a variety of chemical names and trade names, which makes it difficult for the general public to identify them as antibiotics. In China, antibiotic drugs are called anti-inflammatory drugs with misconception or direct chemical names rather than antibiotics. A study on Chinese college students revealed that misinterpreting antibiotics as anti-inflammatory drugs significantly increased self-medication with antibiotics . SimilarConsequently, this study aims to investigate the moderating effect of parental skills for antibiotic identification on the link between parental skills for antibiotic use and inappropriate antibiotic use for children in China Fig. . Our hypth out of 31 provinces in terms of gross domestic product per capita in 2017), Shaanxi , and Guangxi . A representative sample was acquired from the above provinces by implementing multistage stratified random cluster sampling, and successive stages of the sampling procedure included provinces, cities of prefecture level, cities, and rural areas in sequence. The sample population included all parents of children aged 3–13 who attended selected kindergartens and primary schools and all parents who brought their children under the age of 3 to the selected community health service center for routine physical examination and vaccination on weekdays. More specific sampling and recruitment processes have been reported in previous studies . Wi. Wi23]. As presented in Table p < 0.001). Parents with higher education attainment, higher income, and who settled in Zhejiang province had a lower probability of engaging in self-medication. Similarly, noteworthy differences were revealed regarding age and the highest level of education between respondents who asked doctors for antibiotics when seeking care and those who did not (p < 0.001). Highly educated parents and those whose children are younger were less inclined to asking doctors for antibiotics when seeking care. Besides, the rates of self-medication with antibiotics and asking doctors for antibiotics when seeking care were both significantly lower in the respondents with a higher level of skills for antibiotic use (p < 0.001).Significant differences were found in terms of the province, the highest level of education, and average household income between parents who self-medicated their children with antibiotics and those without antibiotics . As is shown in Fig. Among 1944 parents who self-medicated their children in the previous month Table , model 4As is displayed in Table The results of the sensitivity analysis, treating the independent variables as continuous variables, were consistent with the above-mentioned conclusion, suggesting that the moderation is robust to the classification of skills for antibiotic identification and use.To our knowledge, this is the first study to explore the moderating effect of skills for antibiotic identification on the association between skills for antibiotic use and inappropriate antibiotic use behaviors. Our results revealed that the correlation between skills for antibiotic use and inappropriate antibiotic use behaviors including self-medication with antibiotics and asking doctors for antibiotics when seeking care was moderated by skills for antibiotic identification. When the skills for antibiotic use are poor, the higher the level of skills for antibiotic identification, the more inappropriate use behaviors occur instead. Only parents who excelled in both skills were least likely to engage in inappropriate behaviors.g the relatively shallow material content of this campaign [There are global efforts to reduce the inappropriate use of antibiotics through national or regional campaigns. However, studies have shown that the evidence base for many community-based antimicrobial stewardship (AMS) interventions is limited and heterogeneous, and existing cases failed to provide strong evidence to support well-established interventions , 26. Forcampaign . Indeed,campaign .In recent years, there has been a growing call to draw on theories, frameworks, and methods from the behavioral and social sciences to assess how AMS and interventions impact in an effective way. Many behavioral theories view skills as important triggers for behavior change –18 and hAmong antibiotic-related skills including antibiotic identification and use, skills for antibiotic identification are easy to be overlooked particularly. In China, the public's misconception is that antibiotics are equivalent to anti-inflammatory drugs, and which drugs belong to antibiotics largely depends on the experience of the masses rather than scientific guidance , 31. SimOur findings of the moderation effect in this study further reveal the significance of skills for antibiotic identification. For the group with poor skills for antibiotic use, the stronger the skills for antibiotic identification, the more likely the inappropriate behaviors are to occur, likely because although patients clearly know which drugs are antibiotics and effective for their symptoms, they do not know how to use them properly, which leads to unreasonable behaviors such as self-medication with antibiotics. On the contrary, based on poor skills for antibiotic identification, improvements in skills for antibiotic use are often accompanied by increases in inappropriate behaviors. Although patients are able to use drugs correctly, they are unable to identify whether the drugs used are antibiotics or not, also leading to the abuse of antibiotics. Therefore, to solve the problem of self-medication with antibiotics and asking doctors for antibiotics when seeking care, skills for antibiotic identification can no longer be ignored and we propose promoting education on antibiotic identification nationwide in the future.Our findings have several implications for future policies and interventions. From the supply-side perspective, the findings give some directional recommendations on the need to strengthen the simultaneous education of people's multifaceted skills, especially the skills for antibiotic identification. For six consecutive years, the Chinese government has held the "Antimicrobial Awareness Week" in conjunction with the World Health Organization, which is a good opportunity to improve the antibiotic-related skills of the public . AntibioSome limitations should be noted. First, our study relied on parental self-reports, which could lead to recall bias. However, we tried to control this bias by asking parents about their behaviors and children’s symptoms within the recent month rather than longer. Second, the measurement of skills for antibiotic identification only included six questions, which might not be comprehensive enough. Third, our study only enrolled subjects whose parents were primary caregivers, excluding grandparents and other relatives. A children-based study reported that grandparents might be more likely than parents to self-medicate their children with antibiotics empirically in central and eastern China , thus thWithin parental context, skills for antibiotic identification and use are of equal importance to the appropriate use of antibiotics, and are associated with behaviors such as self-medication with antibiotics and asking doctors for antibiotics when seeking care. Skills for antibiotic identification can moderate the association between skills for antibiotic use and behaviors, resulting in a directional change in the correlation. Skill-based tailored educational interventions need to be developed to reduce parental self-medication and demanding behaviors.Additional file 1: Appendix. Table A1. Specific questionnaire items. Table A2. (a)Association between socio-demographic characteristics and parents’ skills for antibiotic identification and antibiotic use among parents who self-medicated their children(N=1944). (b)Association between sociodemographic characteristics and parents’ skills for antibiotic identification and antibiotic use among parents whose children visited hospital(N=2478). Table A3. Correlation analysis between skills for antibiotic identification and skills for antibiotic use among parents who self-medicated their children(N=1944). Table A4. Correlation analysis between skills for antibiotic identification and skills for antibiotic use among parents whose children visited hospital(N=2478). Table A5. Sensitivity analysis. (a) Parents who self-medicated their children(N=1944) (b) Parents whose children visited hospital(N=2478).


After that, a quasi-static concrete damaged plasticity (CDP) model was employed to simulate the influence of inertia on the stress distribution and axial reaction force at the loaded end of concrete under different rates of compressive loading and verified with experimental results. The results obtained in this study indicated that the dynamic nominal strength of concrete obtained from the tests could not be directly used for structural analysis which may overestimate the effect of inertia on the dynamic response of the structure.The rate sensitivity of concrete material is closely related to the inertia and viscous effects. However, the effect of inertia on the dynamic strength of concrete remains unclear. In this paper, digital image correlation technology was applied to study the strain variation of dry and saturated concrete with different loading rates. The test results indicated that the strain gradually decreased with the distance from the load end, and the strain gradient around the load region increased with the strain rate, especially for saturated concrete. Then, a single degree of freedom model was established to evaluate the dynamic compressive strength of elastic concrete. The calculated results indicated that the influence of inertia on the dynamic increase factor (DIF) was negligible for concrete within a low strain rate. When the strain rate is larger than 10 Later, various experimental studies were carried out to quantify the effect of loading rate on the dynamic performance of concrete. Owing to the mechanical properties, geometric dimensions, and curing conditions of the specimens and the test equipment being quite different, DIF (the ratio of measured dynamic concrete strength to static strength during the test) was adopted to identify the effect of strain rate on the strength of concrete. The test results showed that the strength of concrete increases with the strain rate, and the rate sensitivity of concrete with low strength is larger than that with high strength. As the strain rate is increased to a value larger than 100 s−1~101 s−1, a sudden increase in strength can be observed [During the service life of concrete structures, the properties of concrete will be significantly influenced by seismic blasts or impact loading with high loading rates ,2,3,4. Tobserved . Many studies have been conducted to investigate the mechanism of the strain rate on the strength of concrete. For dry concrete, Rossi et al. ,7,8 obseTherefore, the objective of this paper was to investigate the mechanism of inertia on the dynamic strength of concrete. Based on the strain distribution in concrete during the compressive tests, the relationship between dynamic nominal strength and actual strength of concrete was analyzed. Then, the effect of inertia on the nominal strength and actual strength of concrete under different strain rates was evaluated by a single degree of freedom model. Finally, a finite element numerical model based on the static test parameters was established and verified with the test results.According to the test code for hydraulic concrete (SL/T 352-2020), 8 specimens with dimensions of 150 mm × 150 mm × 150 mm were adopted in the tests to study the strain variation of dry and saturated concrete under different loading rates. Therefore, one specimen of each test condition was sprayed with irregular speckles before testing. The maximum aggregate size of concrete was 20 mm, and the mix of proportions by weight was 1: 0.50: 1.48: 2.75 (cement: water: sand: aggregate). The specimens were cured for 28 days after casting. The specimens adopted in this paper can be divided into dry and saturated specimens. For dry specimens, the cured specimens were placed in an oven at the temperature of 90 °C for around 15 days until the weight of the specimens was not changed with the drying time. However, for saturated specimens, the specimens were placed in water until the weight of the specimens was not changed with the immersion time. After the specimens were dry and saturated enough, irregular speckles were sprayed on the testing surface.P and the loading time t of the tests were recorded by the machine system. A CCD camera was set up in front of the specimens to record the surface strain of the specimens under different pressures. The resolution of the camera was 2048 × 2048 and the frame rate was adjusted to fit different loading rates. The VIC-2D system was adopted in the test with the accuracy of 10 uε and developed by the Correlated Solutions INC, USA. Before testing, the accuracy of this VIC-2D system was verified by the strain gauge with an accuracy of 0.5 uε. Tests showed that the error between DIC technology and the strain gauge was within 3%. The specimens were preloaded to 2 kN before the test, and then monotonically loaded till failure.As shown in maxF , the principal strain presented a decreasing trend from the loading end to the fixed end. When the load increased to 80% maxF, strain concentration appeared on the right side of the surface, and a part of the cloud map is missing because of the concrete surface peeling off. When the stress attained the peak loading, a large area of stress concentration appeared on the surface of the specimen and some visible cracks could also be observed.yyε  under different loading stages. For the D1 specimen, the vertical strain gradually decreased from the loading end to the fixed end, and when the load was between 20% and 80% maxF. The value of yyε increased with the compressive loading, and the overall shape of the yyε curves at different loading stages presented similarly. It is worth noting that when the load increased to 90% maxF, the strain concentration appeared around 10~20 mm height of the D1 specimen. The vertical strain at the same point and the time of the strain concentration gradually decreased with the strain but the overall shape of the strain distribution was not significantly changed. Owing to the specimens D1 to D4 being dried before testing, the effect of viscosity on the compressive response of concrete can be neglected. Therefore, the test results indicated that the decreasing trend of the vertical strain even under different strain rates can be attributed to the effect of inertia. As shown in yyε for saturated specimens under different strain rates. It can be observed that the surface strain distribution of the saturated specimens presented a similar trend with dry specimens at the same loading rates. Compared to the surface strains of the dry specimens with the same loading rate, it was found that the strain of the saturated specimens was lower than those of the dry specimens, suggesting that the viscosity provided by the internal free water of the saturated specimens hinders the development of strains in concrete.F is the nominal external load applied to the concrete and can be recorded by the load sensor during the test, iF and vF are the inertial and viscous force acting on the specimen, and their directions are opposite to the acceleration and velocity. Therefore, under the influence of inertial and viscous force, the actual inner force aF exerting on the final failure surface can be expressed asThe dynamic strength test equipment of concrete can be divided into the split Hopkinson pressure bar (SHPB) and the rigidity test machine. The SHPB can provide a large loading rate, but the output is limited. The rigidity test machine can provide a significant output, but the loading rate is limited. It can be seen that no matter what kind of equipment is used to perform the dynamic test, the stress distribution of the specimen can be represented as shown in iF and vF of the material is minimal, and then Equation (1) can be simplified asUnder static loading conditions, due to the long loading time, iF and vF cannot be ignored. Then the actual strength is less than the nominal strength of the material. Therefore, no matter what kind of test equipment is used for dynamic testing, if the measured nominal strength is directly used as the actual strength during the failure process, the dynamic capacity of the structure will be overestimated. Therefore, to accurately analyze the actual properties of concrete strength under different strain rates, the relationship between the nominal strength and the actual strength should be clarified. With a high loading rate, the failure time is very short such that M represents the mass of the concrete, and the spring stiffness K represents the elastic modulus of the concrete. It can be seen that P is the external load provided by the loading equipment on the loaded surface of concrete during the dynamic test. As the loading rate increases up to a specific value, under the influence of inertia, the load imposed on the spring will be different from the measured external load P.A single degree of freedom (SDOF) system is composed of a mass point and a spring is employed to analyze the influence of inertia during the dynamic test. For a concrete structure, as shown in P(t) is the dynamic load acting on the system, which is a linearly increasing function of the loading time, can be expressed asα is the loading rate and t is the loading time. To analyze the influence of the inertia on the system, the impact of damping on the system is ignored. Therefore, the governing equation of the system is expressed as [x is the displacement of the mass point, fx is the maximum value of the spring elongation. From Equation (4), the relationship between spring elongation and load time can be obtained asw is the natural frequency of concrete and can be expressed asAs shown in essed as (4)Mx¨+Kt = t0, x = fx, the external loading applied on the system is αt0, and the actual load on the spring can be shown asP(t0) is the applied load of the test equipment when the concrete is failed and sfF is the actual load on the spring. When the loading rate is high, P(t0) is larger than sfF, and exhibits a rate effect. Then the DIF of the system can be expressed by P(t0)/sfF as shown in Equation (8)It can be seen from Equation (5) that when w = 50 Hz [sfF is close to the applied load P(t), resulting in a marginal effect of inertia on the dynamic strength of concrete. When the loading rate is larger than 1/s, the inertia force exerts a significant influence on the strength of concrete, and then, the concrete fails before it reaches the equilibrium state. Therefore, the DIF is significantly increased with the increase in the loading rate. However, as the strain rate increases to 101/s, DIF attains 21 which is much larger than the dynamic nominal compressive strength of concrete. Thus, another model is needed to simulate the effect of inertia on the dynamic response of concrete.It can be seen from Equation (8) that the influence of inertial force is inversely proportional to the loading time. The shorter the loading time is, the higher the influence of inertia on concrete strength.  = 50 Hz . It can The above single-degree freedom and plane systems can only be used to qualitatively analyze the influence of inertia on the strength of elastic concrete materials under different loading rates. In order to further investigate the inertia influence of concrete during the dynamic tests, a 3D finite element model was established to simulate the dynamic compression response of concrete by ABAQUS software. As depicted in The concrete damaged plasticity (CDP) model proposed by Lee  was applE0 is the initial elastic modulus; ε is the total strain; d is the damage factor. The value of the CPD model parameters used in the concrete is listed in The constitutive equation can be expressed as:−5/s~102/s were considered in the test, where the loading rate of 10−5/s was chosen as a quasi-static loading condition. As shown in Different loading rates, 10The stress cloud diagram at different loading stages is shown in RFdP) is the maximum dynamic axial reaction force of the loading plate, max(RFsP) is the maximum static axial reaction force of the loading plate. The simulation results of concrete are listed in −2/s. As the loading rate increases up to 101/s, the strength of concrete increases by about 24%. By comparing the numerical results of this paper with the CEB bilinear phenomenological empirical formula calculation results, it can be seen from 1/s, the calculated DIF value had a significant improvement, which was close to the calculation result of the CEB phenomenological empirical formula. Therefore, it can be considered that when the loading rate is low (within the seismic rate range), the inertia effect on concrete can be ignored. Owing to the static strength of concrete having been adopted to study the dynamic response of concrete, it can be found in Considering the stress recorded by load sensor is equal to the reaction force of loading plate, thence the DIF values of different strain rates can be expressed as(1)Under the influence of inertia, the stress near the loading end is larger than the far end, and the axial reaction force measured by the actuator is larger than the actual stress in concrete;(2)The effect of inertia on the nominal strength of concrete is related to the strain rate. When the strain rate is less than 1/s, the increase in DIF is small such that the inertial effect on the nominal concrete strength can be ignored, and the rate sensitive is mainly related to the viscous resistance of water in concrete, especially for wet concrete. When the strain rate is larger than 1/s, the nominal strength of concrete is greatly influenced by inertia;(3)In the structural dynamic equation, the effect of inertia on the dynamic response of concrete structures is considered. If the dynamic nominal strength of concrete is directly applied to evaluate the dynamic response of concrete structures, that may overestimate the influence of inertia on the capacity of concrete structures. However, whether the actual strength proposed in this study is appropriately applied, the structural analysis needs to be further studied.In this paper, a single degree of freedom model was established to investigate the influence of inertia on DIF, and a rate-independent elastoplastic damage model of concrete was employed to simulate the actual strength and nominal strength of concrete under different strain rates. The conclusions can be drawn as follows:


Background: A team of infectious diseases physicians, infectious diseases pharmacists, clinical laboratorians, and researchers collaborated to assess the management of lower respiratory tract infections (LRTIs). In 1 sample from our institution, 96.1% of pneumonia cases were prescribed antibiotics, compared to 85.0% in a comparison group. A collaborative effort led to the development of a protocol for procalcitonin (PCT)-guided antibiotic prescribing that was approved by several hospital committees, including the Antimicrobial Stewardship Committee and the Healthcare Pharmacy & Therapeutics Committee in December 2020. The aim of this analysis was to develop baseline information on PCT ordering and antibiotic prescribing patterns in LRTIs. Methods: We evaluated all adult inpatients (March–September 2019 and 2020) with a primary diagnosis of LRTI who received at least 1 antibiotic. Two cohorts were established to observe any potential differences in the 2 most recent years prior to adoption of the PCT protocol. Data  were obtained from the UK Center for Clinical and Translational Science, and the study was approved by the local IRB. The primary outcome of interest was antibiotic duration; secondary outcomes of interest were PCT orders, discharge antibiotic prescription, and inpatient length of stay. Results: In total, 432 patients (277 in 2019 and 155 in 2020) were included in this analysis. The average patient age was 61.2 years ; 47.7% were female; and 86.1% were white. Most patients were primarily diagnosed with pneumonia (58.8%), followed by COPD with complication (40.5%). In-hospital mortality was 3.5%. The minority of patients had any orders for PCT (29.2%); among them, most had only 1 PCT level measured (84.1%). The median length of hospital stay was 4 days , and the median duration of antibiotic therapy was 4 days . Conclusions: The utilization of PCT in LRTIs occurs in the minority of patient cases at our institution and mostly as a single measurement. The development and implementation of a PCT-guided therapy could help optimize antibiotic usage in patients with LRTIs.Funding: NoDisclosures: None


Clostridioides difficile infection (CDI) are often limited in their ability to identify potentially important exposures occurring long before diagnosis. We describe hospitalizations and antibiotic use (AU) occurring up to one year prior to CDI diagnosis among Medicare beneficiaries.Studies describing risk factors for C. difficile test in a person ≥65 years without a positive test in the prior 8 weeks) identified during 2016–2018 through population-based CDI surveillance from four states participating in the Centers for Disease Control and Prevention’s Emerging Infections Program. The analysis included specimens collected in all settings and was limited to case patients who were identified as having fee-for-service Medicare and Part D drug coverage for the year preceding specimen collection. Inpatient hospitalization data was extracted from Medicare Provider Analysis and Review (MEDPAR) files and outpatient AU (prescriptions filled) was determined using Part D drug event files. Timing of hospitalizations and antibiotic prescriptions were described as recent (0–3 months prior to specimen collection) or remote (4–12 months prior).We studied incident CDI cases  filled ≥1 course of outpatient antibiotics in the prior year; 805 (41%) filled an antibiotic both recently and remotely, 497 (25%) only remotely, and 292 (15%) only recently.st generation cephalosporins (10%), and folate pathway inhibitors (10%).Cases with outpatient AU received a median of 23.5 (IQR 12–46) total days supplied, and a median of 2 different antibiotic classes (IQR 1 – 3). The most frequent antibiotic classes filled include fluoroquinolones , 1Overall, 1,314 (67%) cases were hospitalized in the prior year; 569 (29%) were hospitalized both recently and remotely, 446 (23%) only recently, and 299 (15%) only remotely. Median length of stay was 13 days (IQR 6–28).A total of 142 cases (7%) did not have hospitalization or outpatient AU in the prior year, and 1,097 (56%) had both.Incident CDI cases have substantial exposure to recent and remote hospitalization and outpatient AU. Understanding cumulative effects of multiple risk factors can guide prevention strategies, including antibiotic stewardship efforts.Scott Fridkin, MD, Pfizer: Grant/Research Support Ghinwa Dumyati, MD, Pfizer: Grant/Research Support.


Superabsorbent polymers (SAPs) are used as internal curing agents in cementitious materials, which reduce autogenous shrinkage in concrete as they have a low water-to-cement ratios and improve the freeze–thaw resistance. However, the compressive strength of concrete may also be reduced due to additional voids in the hydrated cement matrix. In this study, we fabricated a delayed absorption type of SAP (I-SAP) composed of cross-linked modified acrylate and studied its absorption characteristics and effect on compressive strength after 28 days. Furthermore, the effect of curing conditions on the strength of concrete and hydrated cement paste with SAP were investigated. The absorption capacity of I-SAP in the synthetic pore solution and deionised water was examined and compared with that of a conventional SAP, and the former was absorbed more by I-SAP. The results revealed that the compressive strength of concrete increased with the addition of I-SAP, particularly with the curing condition of 60% RH. Although the compressive strength of hydrated cement paste with I-SAP reduced in water or sealed curing conditions, no loss of strength in the paste cured at 60% RH was seen. The cement matrix densification due to hydration of belite around the SAP surface is the main mechanism for strength development in concrete cured at sealed and 60% RH. However, the voids formed by SAP control the compressive strength of hydrated paste. Superabsorbent polymers (SAPs) are hydrophilic networks capable of absorbing and storing large amounts of water or aqueous solutions and are used in various applications. Recently, SAPs have been used as internal curing agents in cementitious materials for mitigating autogenous shrinkage in ultra-high-performance concrete (UHPC) and HPC, as they have a low water-to-cement ratio ,2,3. SAPDiverse results have been reported in the literature regarding the strength of cementitious materials with SAP. Many studies have reported that the compressive strength of cementitious materials remains constant or is reduced with the addition of SAP ,27,28,29Several solutions have been proposed to limit the water absorption of mixing water and to reduce the loss of compressive strength . When thHere, ordinary Portland cement , chemical composition given in The mix proportions of concrete and its fresh properties are listed in 4·2H2O, Na2SO4, K2SO4, and KOH,  assuming that the concentrations of Ca2+, Na+, K+, and SO42− were 10, 100, 180, and 86 mM, respectively, and pH was 12.8 [The particle size distribution of the SAP was determined using laser diffraction . The water absorption capacity of SAPs in synthetic pore solution and deionised water was determined using the tea-bag method ,21,34,35was 12.8 . The teaThe V-funnel  test was used to determine the appropriate range of filling ability, viscosity, and resistance against the segregation of concrete. Initially, the funnel was filled with approximately 12 L of concrete. After 10 ± 2 s, the gate at the bottom of the V-funnel was opened, and the time taken for the concrete to flow from the funnel to the container below was measured.2, a contact angle of 130°, and applied pressure up to 4.45 psi for measuring pores larger than 3 nm in diameter. For air void evaluation, a linear transverse method in accordance with ASTM C457/C457M was adopted for the hardened specimens from each mixture.The compressive strength of the hardened cement paste and concrete cured for 28 days was measured according to JIS A 1108, formwork JIS A 1132. A mercury intrusion porosimetry (MIP) instrument was used to determine pore size distribution. The hydrated samples were cut into small pieces (approximately 5 mm in size) and dried under vacuum. The selected parameters for mercury intrusion were a surface tension of 485 erg/cmThe cylindrical cement paste specimens cured for 28 days were cut to a diameter of 50 mm × 40 mm height for observation under micro-focus X-ray computed tomography (µCT). The pore structures of the specimens were scanned using the cone beam mode in a µCT scanner “TOSCANER 31300µhd”  with parameters (tube voltage 130 kV and tube current 124 μA). The number of projection directions used in all scans was 1500. In each projection direction, 20 consecutive scans were conducted, and the averaged projection data were used for image reconstruction to reduce the statistical noise caused by the X-ray image intensifier . The num2O3), which is an internal standard substance. They were analysed using X-ray diffraction (XRD), which was performed using a Rigaku MultiFlex X-ray generator  with Cu Kα radiation under the following conditions: tube voltage of 40 kV, tube current of 40 mA, scan speed of 1º2θ min−1, scan range of 2θ = 5–70°, step width of 0.02°, divergence slit of 0.5°, scattering slit of 0.5°, and receiving slit of 0.3 mm. Siroquant Version 4.0  was used for quantitative Rietveld analysis where monotrinic and triclinic C3S, α-C2S, cubic C3A, C4AF, gypsum, portlandite, ettringite, monosulfoaluminate, and corundum were assigned as targets. The number of minerals and the degree of hydration were calculated according to this study [The hydrated samples were broken into pieces using a hammer and immersed in acetone for 24 h to stop the hydration reaction ,39. AfteBackscattered electron images were used to observe the hydration reaction on the surface of the SAP in the samples cured for 28 d at 60% RH. The hydrated cement paste was coarsely crushed and dried with acetone to stop the hydration reaction and then vacuum dried. After one day of vacuum drying, the specimen was cast with epoxy resin and polished with abrasive paper of grid sizes 80, 240, 480, 1000, and 1500. Afterwards, the specimens were polished with diamond paste to a roughness of 0.25 μm. Finally, they were surface-dried and sputtered with platinum. A scanning electron microscope JSM-IT200  was used at an acceleration voltage of 15 kV in the backscattered electron image mode for the measurement. The obtained BSE image was separated into the unhydrated cement part and others using brightness , then itThe cumulative volume and particle size distribution of the SAP particles used in the water absorption experiments are shown in The water absorption behaviour of the SAP particles in the synthesised pore solution and deionised water is shown in The V-funnel flow times of concrete with and without SAP are shown in As discussed in To evaluate the strength gain in concrete and loss in cement paste, the microstructures of the hydrated cement paste and concrete were analysed using various experimental techniques. A wide range (1–10 mm) of pore and void sizes exists in concrete, and thus, at least two methods (MIP and μCT) should be used to evaluate the pore structure in hydrated cement paste with SAP . Figure The XRD/Rietveld results showed that the addition of SAP increased the hydration rate, especially belite, but it should be examined whether the hydration rate increased in the vicinity of SAP or throughout the entire cement matrix. Scanning electron microscopy (SEM) using BSE was conducted for the samples cured in the RH 60% environment, and a significant difference in belite hydration was seen. The results are shown in The presence of air voids in concrete or large voids due to the release of water from SAP could influence the microstructure and eventually the compressive strength. A linear transverse method was used to measure the air voids in the concrete, and the results are shown in The large pores or voids formed by the release of water from SAP could reduce the strength of hydrated cement paste. Because SAP voids were too large to be detected by MIP measurements ,52, μCT I-SAP showed a higher absorption capacity in the pore solution than in deionised water and strongly influenced the compressive strength of concrete and hydrated cement paste.V-funnel time, indicating flowability, was 8.3 times higher for concrete with C-SAP than for plain concrete, whereas it was around 1.85 times higher for plain for concrete with I-SAP.The strength of the concrete with I-SAP increased compared to that without I-SAP under each curing condition, especially for the concrete cured under sealed conditions and 60% RH environment. An increase of 14% and 30% was seen with respect to plain concrete in sealed and at 60% RH curing conditions, respectively.The addition of I-SAP reduced the strength of hydrated cement paste cured in water and sealed conditions. The strength of the I-SAP-added paste in the samples cured at 60% RH was equivalent to that of the plain concrete.Similar air void distribution was seen regardless of the curing method or presence of I-SAP. The porosity of the cement paste decreased with the addition of SAP in the sealed and RH 60% curing conditions, which supports the strength development of concrete.The inclusion of SAP mainly promoted the hydration reaction of belite, suggesting that the water in SAP affects the reaction approximately 50 μm from the SAP surface. Therefore, the strength enhancement of concrete by adding SAP was due to the cement matrix densification.The developed I-SAP can be applicable in producing concrete without adding extra water to mitigate autogenous and drying shrinkage while maintaining or enhancing compressive strength.In this study, a delayed absorption type SAP (I-SAP) was fabricated, and its characteristics and effects on its compressive strength after 28 days were investigated. Moreover, the influence of the curing condition on strength was studied. The following conclusions can be drawn:


The results showed that FM could be partially replaced with SBM and PBM in shrimp feeds supplemented with 0.19% MET-MET or 0.06% MET-MET plus 0.10% B. amyloliquefaciens CECT 5940 without adversely affecting the growth performance and welfare of Litopenaeus vannamei. These results may be interesting for developing low fishmeal feeds and contributing to aquaculture sustainability.The accelerated expansion of shrimp farming requires protein sources with high nutritional value to formulate feeds that satisfy shrimp nutritional requirements. Fishmeal (FM) is the main protein source for aquafeed formulations. However, its limited supply and high cost encourage research on alternative protein sources to formulate more profitable feeds that contribute to aquaculture sustainability. Soybean meal (SBM) and poultry by-product meal (PBM) have been used as protein sources for replacing fishmeal, but their essential amino acids imbalance contributes to low shrimp growth performance and affect shrimp health. Therefore, the study purpose was to evaluate the effect of FM replacement by SBM and PBM in diets supplemented with DL-Met, MET-MET (AQUAVI®), Bacillus amyloliquefaciens CECT 5940 (ECOBIOL®) and their combinations on growth performance and health of juvenile Litopenaeus vannamei. A total of six experimental diets were formulated according to L. vannamei nutritional requirements. A total of 480 shrimp (0.30 ± 0.04 g) were randomly distributed into 24 tanks . Shrimp were fed with control diet  and five diets with 50% FM replacement supplemented with different methionine sources, probiotic (B. amyloliquefaciens CECT 5940) and their combinations: D1 (0.13% DL-MET), D2 (0.06% MET-MET), D3 (0.19% MET-MET), D4 (0.13% DL-MET plus 0.10% B. amyloliquefaciens CECT 5940 and D5 (0.06% MET-MET plus 0.10% B. amyloliquefaciens CECT 5940). Shrimp fed D3 and D5 had significantly higher final, weekly weight gain, and final biomass compared to shrimp fed CD (p < 0.05). Shrimp fed D2 to D5 increased the hepatopancreas epithelial cell height (p < 0.05). Digestive enzymatic activities were significantly increased in shrimp hepatopancreas’ fed D3 (p < 0.05). Meanwhile, shrimp fed D1 had significant downregulation of immune-related genes (p < 0.05). Moreover, shrimp fed D3 and D5 increased the abundance of beneficial prokaryotic microorganisms such as Pseudoalteromonas and Demequina related to carbohydrate metabolism and immune stimulation. Also, shrimp fed D3 and D5 increased the abundance of beneficial eukaryotic microorganism as Aurantiochytrium and Aplanochytrium were related to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) production which plays a role in growth promoting or boosting the immunity of aquatic organisms. Therefore, fishmeal could be partially substituted up to 50% by SBM and PBM in diets supplemented with 0.19% MET-MET (AQUAVI®) or 0.06% MET-MET (AQUAVI®) plus 0.10% B. amyloliquefaciens CECT 5940 (ECOBIOL®) and improve the productive performance, health, and immunity of white shrimp. Further research is necessary to investigate synergistic effects of amino acids and probiotics in farmed shrimp diets, as well as to evaluate how SBM and PBM influence the fatty acid composition of reduced fishmeal diets and shrimp muscle quality. Nevertheless, this information could be interesting to develop low fishmeal feeds for aquaculture without affecting the growth and welfare of aquatic organisms.An 8-week feeding trial investigated the effect of Fishmeal (FM) replacement by soybean meal (SBM) and poultry by-product meal (PBM) in diets supplemented with DL-Met, MET-MET (AQUAVI Litopenaeus vannamei) was the most representative species with 52% of total production [Shrimp farming yielded almost 11.2 million tons in 2022 and Pacific white shrimp  [® has better physicochemical properties such as very low water solubility and higher absorption than DL-Met [Methionine is an EAA scarce in low fishmeal aquafeeds and is necessary for normal growth , proteinMet-Met) . Howevern DL-Met ,14.Bacillus subtilis) supplementation has positive effects on growth performance and health in white shrimp (L. vannamei) and bullfrog (Lithobates catesbeianus) fed low fishmeal feed [Bacillus bacteria are widely used in aquaculture as probiotics because they have the capacity to produce antimicrobial compounds and exoenzymes that improve nutrient digestion, pathogen inhibition, immune response modulation, gut integrity maintenance, and consequently the growth performance [B. amyloliquefaciens has antibacterial activity and produces digestive enzymes that support digestion [On the other hand, it has been reported that probiotics  [®), B. amyloliquefaciens CECT 5940 (ECOBIOL®) and their combinations on growth performance, hepatopancreatic histology, digestive enzymatic activity, transcriptional response of immune-related genes, and the microbial composition of the digestive system of juvenile Pacific white shrimp (L. vannamei).Due to the above, alternative sources to fishmeal, combined with many additives have been used in aquafeeds to guarantee an essential nutrient supply, improve productive performance, preserve the diet’s physicochemical composition, and maintain the aquatic environment’s quality . Hence, rganisms ,8,20,21.chickens  and NileL. vannamei nutritional requirements [B. amyloliquefaciens and their combinations. D1: 0.13% DL-MET, D2: 0.06% MET-MET (AQUAVI®), D3: 0.19% MET-MET (AQUAVI®), D4: 0.13% DL-MET plus 0.10% B. amyloliquefaciens CECT 5940 (ECOBIOL®) and D5: 0.06% MET-MET (AQUAVI®) plus 0.10% B. amyloliquefaciens CECT 5940 (ECOBIOL®). In addition, the water stability ratio was evaluated as a diet’s physical characteristic by a previously described method [A total of six experimental diets were formulated according to the irements  and manud method . The forL. vannamei were obtained from a shrimp farm from Sonora, Mexico. The shrimp were pathogen-free according to procedures described in the Manual of Diagnostic Tests for Aquatic Animals of the World Organization for Animal Health [Juvenile l Health . Before 3). There were four replicate tanks that were randomly assigned for each dietary treatment. Shrimp were fed to satiation with an initial ration of 12% of their biomass divided into three rations during the day  for 56 days, adjusted daily depending on residual feed presence or absence. Temperature (27.84 to 28.36 °C), salinity (36.98 to 37.07 g/L), dissolved oxygen (4.00 to 5.17 mg/L), and pH (7.41 to 7.84) were recorded. Every day, 30% of the water was changed. The uneaten feed, feces, molts, and dead shrimp were removed daily. After a feeding trial and a fasting period of 24 h, three shrimp were randomly sampled from each replicate to obtain 400 μL of hemolymph for gene expression analysis [At the start, 480 healthy shrimp with (0.30 ± 0.02 g) were fasted for 24 h and randomly distributed to 24 circular tanks (volume is 150 L) at a density of 20 shrimp per tank /Final number of shrimps.Weekly weight gain = /Number of weeks.Specific growth rate = 100 × /days of experiment.Survival rate = 100 × .Final biomass = Final weight × Final number of shrimps.Feed intake = Feed Input (dry weight) − Feed collected (dry weight).Feed conversion rate = Feed intake/Final biomass.The shrimp hepatopancreas samples fixed in Davidson’s solution were processed according to the method described by Bell and Lightner . Histolo®, Louis, MO, USA). Amylase activity was measured using soluble starch as substrate [Intestines and hepatopancreas were separately homogenized to 10% ratio with 0.9% saline solution and centrifuged at 3500 rpm for 10 min at 4 °C, and supernatant was immediately analyzed for digestive enzyme assays with a microplate reader . Protease and lipase activities were assayed by commercial kit . cDNA was synthesized with Total RNA (500 ng) using the ImProm-II™ Reverse Transcription System (Promega®) and oligo d(T)20 (T4OLIGO). The cDNA synthesis was realized by reverse transcription at 42 °C for 60 min; then reverse transcriptase was inactivated at 70 °C for 15 min to stop the reaction. The cDNA was diluted with 80 μL of ultrapure water, and 5 μL was used as template for the real time quantitative PCR (qPCR) reaction. Transcriptional response was analyzed from five immune-related genes and β-actin as reference gene . The qPCR conditions were initial denaturation at 95 °C for 10 min, followed by 40 denaturation cycles at 95°C for 15 s, and annealing/extension at 60 °C for 1 min. An analysis of the dissociation curve (60–95 °C) at a temperature transition rate of 0.5 °C/s was performed for each pair of primers. The relative quantification method was used for gene expression analysis according to Rodriguez-Anaya [The hemolymph was centrifuged at 3500 rpm for 10 min at 4 °C to separate the hemocytes from the plasma. The total RNA from hemocytes was extracted with TRIzol Reagent  and treated with RNA-free DNase . Genomic DNA samples were then outsourced to the Microbial Genomics Laboratory  for DNA library preparation and sequencing using standard Illumina protocols for amplification [The genomic DNA from hepatopancreas and intestines of 12 shrimps per treatment was extracted using Quick-DNA™ Fecal/Soil Microbe , following the manufacturer’s instructions. The DNA concentration was quantified using a NanoDrop 2000 spectrophotometer , and DNA quality was evaluated by agarose gel electrophoresis  DNA, eliminating the samples from the hepatopancreas. Therefore, the data presented on eukaryotic microbiota characterization corresponds to the microorganisms present in the intestine. The dataset used were 12,970 sequences and were assigned to 43 ASVs.Illumina sequencing using primers for the V4 hypervariable region in the 16S rRNA gene yielded 976,065 PE reads of 150 bp corresponding to the intestine and hepatopancreas of The growth performance results, hepatopancreas’ cell height, digestive enzymatic activity, and transcriptional response of immune-related genes were evaluated by one-way analysis of variance (ANOVA). If any significance was observed, Tukey’s test was performed for means comparison. Statistical analysis was performed with Statgraphics Centurion XVI. Significance was set at 95% probability levels.p < 0.05), but without statistical difference with shrimp fed D2 and D4 and (p > 0.05). The lowest value of feed conversion rate was observed with shrimps fed D3, but no significant difference was found in FCR among all diet treatments (p > 0.05). While feed intake significantly (p < 0.05) decreased in shrimps fed D1 and significantly increased (p < 0.05) in shrimps fed D5. No significant difference was found in survival rate among all diet treatments (p > 0.05).Growth performance values are presented in p < 0.05) height of the hepatopancreas epithelial cells than shrimp fed CD  than shrimp fed CD, whereas the digestive enzyme activities of intestine were not influenced (p > 0.05). In hepatopancreas from shrimp fed D1 the lowest value of amylase and lipase was observed, while in intestine the digestive enzyme activities had the lowest values but no significant differences (p > 0.05) were observed compared with shrimp fed CD.The effect of different dietary methionine sources and p < 0.05) upregulated in shrimp fed D3 and D5. LGBP was significantly (p < 0.05) upregulated in shrimp fed D2 and D3. MnSOD was significantly (p < 0.05) upregulated in shrimp fed D2, D3 and D5. HSP60 was significantly (p < 0.05) upregulated in shrimp fed D5. The lowest values of transcriptional response of immune-related genes were observed in shrimp fed D1 compared to all dietary treatments.The transcriptional response of immune-related genes of white shrimp fed reduced fishmeal diets with additives was determined and compared with the shrimp fed CD . Except The rarefaction curve analysis showed that the observed species per sample was sufficient for both 16S-V4 A and 18SThe experimental diet’s effects on microbiota structure were determined using UniFrac distance and visualized using PCoA plots. The results revealed clear separation among experimental diets, but without significant differences in prokaryotic communities from intestine or hepatopancreas C as wellPseudoalteromonas was the most prevalent in shrimp intestine while Demequina was the most prevalent in shrimp hepatopancreas. Demequina had a low increase in shrimp intestine fed D3 and D5, whereas Lysinimicrobium and Ruegeria were increased in shrimp hepatopancreas fed D3 and D5  phylum was the most prevalent in all shrimp intestines, however an increase in the Opisthokonta phylum was observed in shrimp intestines fed D5 A. At thes fed D1 B.L. vannamei, such as shrimp feed with 5% to 10% fishmeal and supplemented with a level between 0.15% and 1.7% of MET-MET (AQUAVI®) or 3% of DL-MET [L. vannamei) with initial weight 0.98 ± 0.02 g, suggested 0.20% MET-MET (AQUAVI®) for better growth performance when shrimp were fed reduced fishmeal feed [B. amyloliquefaciens (104 and 103 UFC/mL) dissolved in water of a biofloc system for farmed L. vannamei were reported [L. vannamei growth performance. Therefore, this study evaluated the effect of FM replacement by SBM and PBM in shrimp diets supplemented with 0.13% of DL-MET (D1), 0.06% of MET-MET (D2), 0.19% of MET-MET (D3), and according to the manufacturer recommendations we used combinations of 0.13% of DL-MET plus 0.1% B. amyloliquefaciens CECT 5940  (D4) and 0.06% of MET-MET plus 0.1% of B. amyloliquefaciens CECT 5940 (D5). All reduced fishmeal diets supplemented with methionine sources and probiotic showed good water stability values. Therefore, the fishmeal reduced diets evaluated in this study are in accordance with previous reports and all dietary treatments showed a good response in shrimp growth performance. Nevertheless, shrimp fed D1 had lower performance parameters, while shrimp fed D3 and D5 had higher performance parameters. The significant low growth performance in shrimp fed D1 can be related to poor feed intake due to methionine deficiency causing palatability reduction in reduced fishmeal aquafeeds [B. amyloliquefaciens CECT 5940. The high growth performance could be due to the probiotic’s beneficial properties, which include antimicrobial activity and production of α-amylase, cellulase, and protease that increase the nutrients digestibility and absorption [B. amyloliquefaciens is a methionine producer [B. amyloliquefaciens CECT 5940 could improve the nutrient utilization and consequently the shrimp growth performance. It is important to note that SBM and PBM have high levels of fatty acids, but n-3 long-chain polyunsaturated fatty acids are deficient in these protein sources [Previous studies have evaluated the effects of reduced fishmeal diets supplemented with different dietary methionine sources on growth performance of f DL-MET ,20,42,43reported ,45, but quafeeds . Shrimp sorption . Also, aproducer  and thisproducer ,49,50 anproducer . Therefo sources . In thisB. amyloliquefaciens in reduced fishmeal diets, increasing B cell, influencing digestive enzyme secretion, nutrient absorption and assimilation, and feed utilization as reported in other studies when used fishmeal alternative sources and additives [B. amyloliquefaciens in L. vannamei hepatopancreas.The shrimp hepatopancreas is a digestive organ and plays an important role in digestive enzyme secretion, nutrient transport, storage, and absorption, therefore, its function is key to shrimp growth performance and health ,53. Howedditives ,56,57,58p < 0.05) in hepatopancreatic digestive enzyme activity compared between all groups, and no significant differences were found in the intestinal digestive enzyme activity. Overall, low digestive enzyme activities were noticed in both organs from shrimp fed D1. In agreement with these results, methionine supplementation increased digestive enzymes activities in red sea bream (Pagrus major) [Ctenopharyngodon idella) [L. vannamei) [Labeo rohita) [B. amyloliquefaciens on shrimp digestive enzyme activity have not been reported in L. vannamei but it is known that probiotics increase the digestive enzymes’ activity and improve the feed utilization and digestion [The enzyme digestive activity is a physiological process that improves nutrient digestion and absorption, and therefore, is a key factor for promoting shrimp growth performance . Neverths major) , grass c idella) , white sannamei) ,3,20, an rohita) . The effigestion . In addiigestion ,50. Neveigestion . This stDicentrarchus labrax) was fed low fishmeal supplemented with a DL-Met level 12% below their established requirement [L. vannamei) [O. niloticus) [O. niloticus) fed low fishmeal diets supplemented with Spirulina platensis and B. amyloliquefaciens had enhanced immune response and antioxidant capacity, but diminished stress tolerance [The transcriptional response of immune-related genes is very important to obtain data concerning the shrimp health status . Howeveruirement . Also, tannamei)  and Nileloticus)  were fedolerance . The resL. vannamei using 16S and 18S sequencing. The study results suggested that diversity and structure of the microbiota (prokaryotic and eukaryotic) were not different between dietary treatments. However, beta diversity comparison determined that intestinal prokaryotic microbiota clustered separately from hepatopancreatic prokaryotic microbiota, suggesting a unique ecological niche according to shrimp digestive organ [The shrimp digestive system hosts microorganism communities dominated by bacteria, but eukaryotic microorganisms may also be present, building a large microbial ecosystem called the microbiota . The shrve organ . Therefove organ . As willPenaeus monodon) [Pseudoalteromonas belonging to the Proteobacteria phylum, is a digestive enzyme  producing microorganism that contributes to the nutrient digestion of shrimp [Ruegeria, belonging to the Proteobacteria phylum, produces triesterase activity, contributing to host digestive processes as well as antibacterial activity against Vibrio anguillarum [Demequina belonging to the Actinobacteria phylum can produce α-amylase, xylanase, and cellulase, which are involved in carbohydrate absorption and utilization [Lysinimicrobium can be considered a subjective synonym of Demequina [B. amyloliquefaciens) would help the beneficial roles of prokaryotic communities on the shrimp digestive system.According to the abundance of prokaryotes in all intestines and hepatopancreas samples, the most prevalent phylum was Proteobacteria while the Actinobacteria phylum had a higher presence in hepatopancreas samples. These results are in accordance with a previous study , and it monodon) . Pseudoaf shrimp ,78,79; if shrimp ,81. Rueguillarum . Demequilization ,84,85,86emequina  and consemequina . TherefoL. vannamei DNA was detected in this study. Furthermore, it is common in fecal DNA metabarcoding that microeukaryotes’ DNA in feces is degraded more rapidly than the host´s DNA and additional steps such as cleavage or blocking host DNA using restriction enzymes or blocking primers is necessary before, or after amplification [Aurantiochytrium had higher abundance in shrimp intestine fed D3 while Aplanochytrium was most abundant in shrimp intestine fed D5. Additionally, Ebria was the most prevalent in shrimp intestine fed D1. Aurantiochytrium is an eicosapentaenoic acid (EPA) producer [Aplanochytrium produces docosahexaenoic acid (DHA) [Ebria has an internal solid siliceous skeleton, which could result in poor digestion by aquatic organisms [Ebria abundance affecting productive performance and health of shrimp, while diets supplemented with 0.19% MET-MET or 0.06% MET-MET plus 0.10% B. amyloliquefaciens would help the beneficial roles of eukaryotic communities in the shrimp digestive system.It was difficult to characterize the eukaryotic microorganism abundances with 18S gene sequencing, because a great amount of fication . Neverthproducer  whereas id (DHA) . These fid (DHA) . On the rganisms , which crganisms . Howeverrganisms . This agB. amyloliquefaciens CECT 5940 without adverse effects on growth performance. In comparison with control diet, shrimp fed reduced fishmeal diets with 0.19% MTE-MET and 0.06% MET-MET plus 0.10% B. amyloliquefaciens CECT 5940 had 43% and 40% more final biomass, respectively. Moreover, shrimp fed reduced fishmeal diets supplemented with MET-MET and/or B. amyloliquefaciens CECT 5940 had better hepatopancreas epithelial cell height, digestive enzyme activity, transcriptional response of immune-related genes, and beneficial microbiota for the digestive system. Further research is necessary to investigate graduated levels of methionine sources and synergistic effects of amino acids and probiotics in reduced fishmeal diets for farmed shrimp. Also, it would be interesting to evaluate how SBM and PBM influence the fatty acid composition of reduced fishmeal diets and shrimp muscle quality. Nevertheless, this information could be interesting to develop low fishmeal feeds for aquaculture without affecting the growth and welfare of aquatic organisms.Fishmeal could be partially replaced up to 50% by SBM and PBM in shrimp feed supplemented with MET-MET and/or


Bacterial resistance to antibiotics continues to be a global public health problem. The choice of the most effective antibiotic and the use of an adapted dose in the initial phase of the infection are essential to limit the emergence of resistance. This will depend on (i) the isolated bacteria and its resistance profile, (ii) the pharmacodynamic (PD) profile of the antibiotic used and its level of toxicity, (iii) the site of infection, and (iv) the pharmacokinetic (PK) profile of the patient. In order to take account of both parameters to optimize the administered treatment, a minimal inhibitory concentration (MIC) determination associated with therapeutic drug monitoring (TDM) and their combined interpretation are required. The objective of this narrative review is thus to suggest microbiological, pharmacological, and/or clinical situations for which this approach could be useful. Regarding the microbiological aspect, such as the detection of antibiotic resistance and its level, the preservation of broad-spectrum β-lactams is particularly discussed. PK-PD profiles are relevant for difficult-to-reach infections and specific populations such as intensive care patients, cystic fibrosis patients, obese, or elderly patients. Finally, MIC and TDM are tools available to clinicians, who should not hesitate to use them to manage their patients. The increasing resistance of bacteria to antibiotics is a major worldwide public health problem, particularly considering the association of increased mortality and length of hospital admission for patients with multidrug-resistant (MDR) bacterial infections . It is uBefore targeting an optimal antibiotic therapy, an empirical treatment is administered, and the previous collection of a microbiological sample helps choose the most effective treatment. Among the microbiological results, antibiotic susceptibility testing (AST) is currently based on testing the ability of an antibiotic to inhibit bacterial growth in vitro under standardized experimental conditions. Antibiotic susceptibility is mostly measured by the diameter (in mm) of the zone of bacterial growth inhibition around an antibiotic-containing disk versus the tested pathogen. AST reflects the responsible pathogen’s susceptibility or resistance to diverse antibiotics, leading to the selection of a clinically effective antimicrobial treatment. For most bacterial infections, AST measured using a diameter is sufficient. However, in the case of severely ill patients with chronic infections previously treated with many broad-spectrum antibiotics, more accurate information is needed to facilitate the selection of an optimal antibiotic regimen. The minimal inhibitory concentration (MIC) may help to choose the most appropriate treatment. It defines in vitro the levels of susceptibility or the resistance of specific bacterial strains to a targeted antibiotic . HoweverClassic AST, e.g., critical diameter measurement, raises problems in some conditions, leading to the determination of the MIC value. We will detail below the methods that can be used, their relevance, and their microbiological indications. Two main methods are used to determine MIC . Broth mClassic AST raises problems in certain conditions, leading to the need to perform a specific MIC measurement. We will detail below the microbiological indications, their limits, and the methods that can be used. In addition, the microbiological relevance of MIC determination is summarized in For some antibiotics, the agar diffusion method (disc and gradient strip) does not allow for the interpretation of the susceptibility of the tested microorganisms. This is due to their poor diffusion in a solid medium (colistin) or the need for particular chemical conditions  . TherefoStreptococcus pneumoniae resistant to oxacillin  and Haemophilus influenzae resistant to aminopenicillins. For some microbiological species, it is difficult in the case of resistance to the usually tested antibiotic to define the resistance mechanism and to specify the optimal treatment choices. This is the case for β-lactam resistance in S. pneumoniae, resistance is associated with alterations in penicillin-binding proteins (PBPs) that reduce the binding affinity of the antibiotic to PBPs [S. pneumoniae genome encodes six PBPs and each β-lactam inhibits different PBPs, the modification of PBPs leads to an increase in the MICs of all β-lactams, but the extent of this increase varies according to the antibiotic [In the first case, for  to PBPs . As the tibiotic . H. influenzae), two main mechanisms of amino penicillin (AMP) resistance lead to reduced susceptibility to this antibiotic class: either by the production of a β-lactamase, or by alteration of PBP3 [Whereas in the second case ( of PBP3 . In addi of PBP3 . S. pneumoniae) or AMP (H. influenzae). EUCAST guidelines recommend testing of the β-lactams of interest, particularly in these cases [Determination of the MIC of β-lactams to define the most appropriate treatment will be more justified when a practitioner is dealing with severe or invasive infections (such as bacteremia or meningitis), clinical failure, and/or an isolate suspected of reduced susceptibility to penicillin  of the topoisomerase genes [Salmonella typhi or non-typhoidal Salmonella isolates with ciprofloxacin MICs of 0.125 to 1.0 mg/L have more treatment failures and longer times to fever clearance than patients with isolates fully susceptible to ciprofloxacin (MICs < 0.06 mg/L) [Fluoroquinolone resistance in se genes  that lease genes . Indeed,06 mg/L) . Thus, u06 mg/L) . Staphylococcus aureus (MRSA) infections is vancomycin, which continues to be the reference standard approach in this context. However, an increasing number of MRSA isolates with high MICs, within the susceptible range (vancomycin MIC creep), are being reported worldwide. It has been reported that the efficacy of vancomycin therapy is contingent upon a target AUC0–24/MIC ratio of ≥400 (see next section on PK/PD indices) [S. aureus isolate if the vancomycin and/or teicoplanin MIC is >1 mg/L, using the BMD method [The first option for the treatment of invasive methicillin-resistant indices) . Neverthindices) . Moreoveindices) ,23. Diveindices) ,21 and tPiperacillin-Tazobactam/Cephalosporins and ESBL-Producing StrainsEscherichia coli [Escherichia coli strains or Klebsiella pneumoniae-related infections with MICs below 1 mg/L [Carbapenems have been considered as the treatment of choice for severe infections caused by extended spectrum β-lactamase (ESBL)-producers ,26. The hia coli  and thathia coli ,34. Howew 1 mg/L . In concw 1 mg/L .Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria [The release of new antibiotics has opened up many new possibilities in the treatment of CPE-related infections . Indeed,bacteria ,40. The aim of TDM is optimization of the dose regimen to maximize treatment efficacy while reducing the risk of toxicity and the emergence of bacterial resistance . HoweverfT>MIC), (ii) concentration-dependent antibiotic in which it is the ratio of maximum antibiotic concentration (Cmax) to MIC (Cmax/MIC), and (iii) mixed-effect antibiotics in which %fT>MIC and Cmax/MIC are of interest and are characterized by the ratio of the free drug area under the concentration–time curve during a 24-h period to MIC (fAUC0-24/MIC) [These targets are based on the classically described PK-PD indices with (i) time-dependent antibiotics for which the index of interest is the percentage of time the free drug concentration remains above the MIC (%-24/MIC) ,43. The An a priori dose regimen adaptation—before TDM—should follow recommendations for a specific population and clinical setting, and one way to determine the initial dosage is to review the probability of target attainment (PTA) corresponding to our specific situation . PTA is A posteriori adaptation using concentration measurement is thus recommended for many antibiotics . HoweverToxicity due to overdosage may occur for antibiotics with a narrow therapeutic range and/or in the case of organ failure, especially the kidney, as most antibiotics are renally cleared . In the min < 22 mg/L if used by intermittent infusion and a steady-state concentration (Css) < 35 mg/L if used by continuous infusion [Pseudomonas aeruginosa infection, the EUCAST clinical breakpoint is equal to 8 mg/L, implying a therapeutic target between 32 mg/L (because of a PK-PD target of 100% fT>4x MIC) and 35 mg/L if used in continuous infusion [For β-lactam antibiotics, cefepim is of the greatest concern for neurological toxicity, with a threshold of Cinfusion ,45. So, infusion ,11. In tEnterobacterales, for which the concentrations should be greater than 2 mg/L, but less than 2.4 mg/L when considering the clinical breakpoint [Similar concerns exist for colistin and eakpoint ,57,66. CR) higher than 130 mL/min/1.73 m², occurs in 20% to 65% of ICU patients, and corresponds to an increase in renal blood flow that often arises in septic shock [CR > 90 mL/min, a high dose of 24 g per day by continuous infusion did not achieve 100% fT>4x MIC against bacteria with MIC ≥ 4 mg/L [The use of recommended doses may be associated with sub-therapeutic exposure, particularly in intensive care patients . A speciic shock ,68. It cic shock . This st≥ 4 mg/L . In thisTDM is mainly performed on plasma samples and may not reflect antibiotic exposure at the site of infection, particularly in cases of endocarditis, mediastinitis, central nervous system infections, pneumopathy, or infections on prosthetic material . It is tDirect measurement at the site of infection, when possible, is also interesting and allows for a direct comparison of an antibiotic concentration with the MIC of the offending organism. This has been described, for example, for cefotaxime in peritoneal fluid, meropenem in cerebrospinal fluid, and colistin in drainage fluid in the context of prosthesis infection ,72,73.For a long time, therapeutic monitoring of antibiotic prescriptions was limited to treatments with a narrow therapeutic index (aminoglycosides and glycopeptides) in order to avoid any treatment-related toxicity. Over the last 20 years, numerous publications have suggested the importance and value of monitoring plasma antibiotic levels to cure the infected patient and avoid the emergence of resistance that may be responsible for therapeutic failure or recurrence. Numerous populations at risk of antibiotic underdosing have been described in the literature, both in the ICU ,75,76 anHowever, few publications have evaluated the importance of MIC determination in the outcome of infected patients, even though the antibiotic dosage cannot theoretically be interpreted for a given patient in the absence of MIC. Indeed, difficulty in obtaining the MIC, uncertainties related to the interpretation of this test, and delays in obtaining the results are, in our opinion, the three elements that make the use of this test difficult in clinical practice. Thus, most of the studies carried out to date and demonstrating or suggesting the interest of the MIC determination have been based essentially on a “theoretical” MIC, generally the highest MIC for the chosen antibiotic and found in the species responsible for the infection. This choice, which currently seems to be accepted by various authors, does, however, run the risk of individual toxicity and of collective antibiotic overconsumption. Therefore, the question of the interest of MIC determination in clinical practice is the same as the question of the right prescription, i.e., the right antibiotic dose that best responds to the PK/PD data, for a given microbial species, in a particular tissue infection and in a patient with his/her own specificities. It is thus obvious that many infections will not require antibiotic dosing or MIC determination, provided that the antibiotic administered at the usual doses diffuses to the infection site at sufficient concentrations and below toxic concentrations, concentrations that are equivalent to and exceed the PK/PD parameters (see above) required to cure and avoid the emergence of antibiotic resistance. S. pneumoniae [Staphylococci [Nevertheless, there are still many clinical situations that do not meet the above-mentioned characteristics and for which MIC determination should be considered. Indeed, the literature data lead us to propose a strategy that mainly includes the three main actors: the infectious site, the microbial species, and the antibiotic . Moreoveeumoniae , with reeumoniae , such asylococci , we thinylococci , or in mylococci .Pseudomonas aeruginosa; Burkholderia cepacia), to the presence of biofilm, and to an increase in distribution volumes [There are certainly other clinical situations that require TDM, whether in intensive care, where numerous studies have highlighted the risk of therapeutic failure linked to underdosing, or in special populations such as the very obese (risk of underdosing); the elderly with an increased risk of toxicity ; and fin volumes . It is important to emphasize that certain complex clinical situations involving changes in renal function and infections with species that are difficult to treat will require plasma assays and MIC measurements. In the case of renal failure in a patient infected by a bacterium with a high MIC, the need to reach the required thresholds may lead to exposure of the patient to increased toxicity . On the Enterobacterales, with a hydrolyzable β-lactam, provided that the concentration at the site of infection meets the PK/PD criteria, i.e., in this particular case, a concentration that is more than 40% of the time in the dosing interval above MIC. It is obvious that therapeutic success as well as the risk of failure in this type of indication depend on the MIC value, as was recently recalled in the MERINO study [An indication that, in our opinion, will be more and more frequent lies in the use of antibiotics ”concerned by the resistance mechanisms” of the treated species. Over the last ten years, in view of the spread of resistance and to avoid the use of so-called last-resort antibiotics, the possibility of using narrower-spectrum antibiotics based on phenotypic resistance data has become widespread. Until the worldwide spread of ESBL strains, the genotypic character had prevailed. Thus, species producing an enzyme that hydrolyzes β-lactam antibiotics made it impossible to use these β-lactam antibiotics. Concerning ESBL, it was thus unimaginable to use antibiotics that could be hydrolyzed by the enzyme, such as 3GC. Thus, carbapenems, the only antibiotics that cannot be hydrolyzed by ESBL, were the reference antibiotic. More recently, many authors ,90,91,92To conclude, in TDM implies the use of an available, timely, and accurate bioanalytical assay for drug measurements. Many hospital laboratories now routinely measure the most commonly used antibiotics, most often by immunoassay (notably for aminoglycosides and glycopeptides) or by liquid chromatography coupled to ultraviolet or mass-spectrometry detection . Howevermin, if not available [Once the plasma concentration is obtained and compared to the MIC, dose adjustments may be necessary. For this there are several strategies, from the most complex to the simplest. In recent years, many precision dosing software programs have been developed to optimize antimicrobial dosing . These pvailable . Howevervailable . To dateDetermination of the MIC value has a few limitations. First is the time needed to obtain the AST result. The current widely used methods require 2 days and this may extend the duration of inappropriate initial antibiotic therapy and can negatively impact patient outcome, particularly when bacteremia is associated with septic shock . Second,The microbiological and pharmacological tools already available are useful for the treatment optimization and follow-up of serious infections. The implementation of these tests depends on a number of criteria that we tried to list without being exhaustive . We part


Conclusions: This study identified a low prevalence of antimicrobic consumption in LTCFs. Further surveillance studies are warranted to identify trends and changes in pathogen incidence and antimicrobial resistance and to inform public health authorities on the necessity of prudent use of antimicrobials in LCTFs.Background: Almost half of antimicrobial prescriptions in long-term care facilities (LTCFs) is inappropriate. This broad use might represent a strong contributor to antimicrobial resistance in these facilities. This study aimed to assess antibiotic use patterns and potential associated factors with a survey of LTCFs in the local health authority (LHA) of Novara. Methods: A cross-sectional study was conducted in 25 LTCFs in the LHA of Novara following the healthcare-associated infection in LCTFs (HALT) protocol. Information on residents and facilities was assessed. Antibiotic usage and potential determinants were also estimated. Results: In total, 1137 patients were screened for antibiotic usage. Mean age was 84.58 years (SD 9.77), and the majority were female (76.52%). Twenty-six were antibiotic users . Antimicrobials were mainly prescribed orally (84.62%). Potential risk factors for antibiotic prescription were catheter use (central and peripheral venous,  In recent years, in most European countries, a significant increase in life expectancy in the population aged 65 years has been registered, leading to an ever-growing and fast rise in the request for elderly healthcare services, such as home care, nursing homes, and healthcare facilities . These fAccording to a recent survey performed by the Italian National Statistical Institute (ISTAT), in Italy, the elderly represents 23.5% of the entire population .The population projections performed by the EU Centre for Disease Prevention and Control (ECDC) estimate a certain increase in the number of residents in long-term care in almost all other European countries in future decades, in line with the previously described situation in Italy. Specifically, by 2050, the number of people aged over 65 per 100 people of working age will reach 50%, and the population aged 80 years and over is projected to increase from 16.8 million (4.1%) in 2010 to 43.3 million (11.5%) in 2060 [Patients living in healthcare facilities are usually frail, vulnerable, and at high risk of infection due to their age, age-related health problems, and also because of living in closed facilities in strict contact with other residents .Immunosenescence, comorbidities, and malnutrition—pathological conditions very common among elderly patients—contribute largely to the burden of healthcare-related infections (HAIs), which represent an important issue and concern in long-term care facilities (LTCFs) due to their high prevalence and incidence .The most commonly reported infections are urinary tract infections (UTIs), lower respiratory tract infections, skin infections, and gastroenteritis, among others .HAIs are listed among the main causes of antibiotic prescribing. A recent systematic literature review showed that antibiotic usage in LCTFs is common, and its annual prevalence rates range from 47% to 79% each year ; this reAntimicrobial resistance represents a significant public health concern in LCTFs due to its high mortality and impact on the health system, causing several patient safety issues . Recent Antimicrobial stewardship in nursing homes is a recent but essential concept created to limit the further development of resistance; strategies settled in acute care settings may be adapted to the specific LTCF context .The first step toward improved antimicrobial prescribing is to analyze the current patterns of antimicrobial use.To quantify them, the ECDC has started surveillance, ushering in an effective project known as healthcare-associated infection in LCTFs (HALT) in 2010, a point prevalence survey aimed to provide a deeper insight into antibiotic prescribing patterns in European LTCFs .Italy was included in the 2013 HALT-2 and in the 2017 HALT-3 studies .Quantifying the prevalence of antibiotic prescribing and consumption in LCTFs is warranted to better understand the determinants and the magnitude of this phenomenon, informing local health authorities and administrators on their prudent use.Surveys might represent a helpful tool in the fields of epidemiology and public health to give an overall picture of antimicrobial use in LCTFs, due to minimal resources within those facilities that aim to conduct constant surveillance of antibiotic prescribing .Different from previous similar investigations mostly conducted in entire nations and in facilities with mixed populations, the current study aimed to bring particularly focused evidence on this issue.Our aim was to assess the prevalence and the potential factors associated with antibiotic usage through a point prevalence survey on residents in LTCFs in the territories of a small administrative entity (LHA of Novara) in order to guide local stewardship programs on the appropriate use of antibiotics and on the need for guidelines available on this theme in LCTF protocols.A cross-sectional study was conducted on LTCFs in the LHA of the Province of Novara. This survey was conducted and initiated under the supervision and control of the healthcare-associated infection control team of the LHA of Novara , including towns and municipalities of different sizes with a population of 428,535 as of 31 December 2019.An LHA is an administrative territorial entity of the National Health Service in Italy introduced by the National Health Service Reorganization Act of 1992 .The LHA of Novara is divided into three health sanitary districts: (i) Novara city, (ii) south area, and (iii) north area. In the territory of the LHA of Novara, there are 42 LTCFs.A map of Novara province is shown in An LTCF could be defined as an institution in which medical doctors’ and nurses’ care is guaranteed to patients 24 h a day.All LTCFs belonging to the Novara LHA were invited to join the study, and all residents who were present on the day of the survey were eligible for inclusion.Residents were defined as people who were living in an LTCF for at least 48 h before the day of the survey. Residents who were not living full-time in the LTCF  or living full-time in the LTCF but who were not present on the day of the survey  were excluded from the study.Data were collected through a questionnaire administered to the LHCs’ personnel between the 20 and 27 February 2022; no direct involvement of patients was required.The study was revised by the ethical committee of the LHA of Novara. All procedures conducted in this study followed the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.The questionnaire used for data collection was an adapted version of the HALT protocol of the ECDC  LTCFs pet-test (continuous variables) were also used in order to evaluate the potential association between LTCF residents’ demographic and clinical characteristics and the probability of antibiotic usage. The prevalence of antibiotic use and corresponding 95%CI was also calculated, stratified by the variables associated with antibiotic use, to better appreciate the difference between patients’ characteristics.Descriptive statistics were used to summarize LTCF and resident characteristics. Continuous variables were reported as mean and standard deviation (SD) or median and interquartile range (IQR) if not normally distributed, and categorical variables as absolute frequencies and percentages. The prevalence of antibiotic use was estimated as the ratio between the number of antibiotic users and the number of subjects living in the LTCF who were present on the day of the survey. Exact 95% confidence intervals (95%CIs) were also calculated. Prevalence, overall and stratified by district, was estimated. Chi-squared test, Fisher exact test, or The individual address records and the position of LCTFs in Tests were two-tailed, and the type I error was fixed at 0.05. All statistical analyses herein reported were performed using SAS v 9.4  and R v 3.4.1 .Overall, 25 out of the 42 LCTFs invited to take part in the study actually provided the requested information, corresponding to 1137 residents. LCTF characteristics are reported in Most LCTFs included in our study were located in the north area district and were almost of similar size, with a median number of available and occupied beds of 58 (IQR 35–65) and 41 (IQR 33–57), respectively. We only report on two LCTFs with fewer than 10 patients. Residents in these facilities were followed by a median number of 16 medical assistants and a median number of 4 nurses; 1 physician was available for all LCTFs. The median age of the residents included in our analysis was 84.85, and the majority were female.The prevalence of antibiotic use and the corresponding exact 95%CI, overall and stratified by district, is reported in Of the 1137 residents, 26 were antibiotic users and received at least one antimicrobial agent on the day of the survey; therefore, we revealed a corresponding prevalence rate of 2.29% (95%CI 1.50–3.33). No significant differences were observed between the three sanitary districts of the Novara LHA; specifically, the prevalence-specific estimates varied from 2.14% for the Novara city district to 2.60% for the southern area.The most common HAI was respiratory tract infection, with a relative frequency of 59.09% (n = 13), followed by urinary tract infection . Skin/wound infections, surgical site infections, gastrointestinal tract infections, and genital tract infections were observed equally in 4.55% of residents on antimicrobial treatments on the day of the survey. The lack of antimicrobial results for HAI testing concerned the majority of HAIs , as a diagnostic test was performed for only 37.5% of HAIs.The sputum was the commonest sample and diagnostic material used to diagnose the infection. All the residents on antimicrobial treatment were dispensed one antibiotic on the day of the survey. None of them received more than one antimicrobial agent. Antimicrobials were mainly prescribed orally. Indeed, 84.62% of residents on antimicrobial treatment received antimicrobial treatment per oral administration, while the parental route was used for only four patients (intravenously and intra-muscularly). None of the LCTF residents received antibiotics per nasogastric tube or percutaneous gastric tube; in addition, a nasal or rectal administration route was not reported. In addition, antimicrobial agents were mainly prescribed within the same LCTFs.The most reported indication for the prescribed antimicrobials was for treatment (84%); only 12% of residents received treatment with antibiotics for prophylaxis. The indication was missing and not reported for just one subject. According to the patient charts, antibiotics were mainly prescribed empirically , and only five residents (20%) received targeted therapeutic antibiotics. The median treatment duration was 6 days. Penicillins with beta-lactamase inhibitors and macrolides represented the most prescribed group of antibacterial . Within those groups, specifically, amoxicillin/clavulanate (n = 5) was the most prescribed antibiotic, followed by azithromycin. Fluoroquinolones (levofloxacin and ciprofloxacin) were the third most prescribed antibiotics (three subjects). Antibacterials for systemic use accounted for 15% of all antimicrobial prescriptions. Six out of eight residents who received antibiotics, with available information on the agent, were colonized with SARS-CoV-2, and only one with Klebsiella pneumoniae.The distribution of LCTF residents’ clinical and demographic characteristics is reported in A total of 97 subjects (1 antibiotic user and 96 nonusers) had missing values for all patient demographic and clinical characteristics. Among the remaining 1040 subjects (25 antibiotic users and 1015 nonusers), the mean age of included subjects was 84.58 years (SD 9.77), and the majority were female (76.52%). Disorientation and dementia were present in 502 residents (50.91%). Pressure sores affected 5.97% of residents; moreover, 630 patients (60.58%) were in a wheelchair, and 2.60% were immobilized and bedridden. Few residents had a nasogastric probe, and four were on dialysis treatment; 6.63% of residents needed a urinary catheter, while 2.89% needed a peripheral intravenous one. Finally, nine residents had previous surgery (0.87a), and only 0.87% were hospitalized within the 48 h prior to the days of the survey.p-values 0.0475 and 0.0034, respectively, and urinary, p-value 0.0008), immobilization , and sex . Specifically, subjects using catheters had a higher probability of being antibiotic users and immobilized patients, while females were less frequent antibiotic users. For variables associated with antibiotic use, the prevalence of antibiotic users and the corresponding 95%CI for each stratum are reported in Only a few factors were associated with antibiotic usage: catheter use  ,24.To our knowledge, a focus on small administrative entities, such as a single LHA, was less frequent.The current survey revealed antibiotic consumption in LCTFs in the territories of Novara LHA below the prevalence estimated by a narrative review published recently (3–11%) and 2.6% lower than the prevalence rate that emerged from the most recent survey performed in 24 European countries and 2 European candidate countries ,26.The first study on antibiotics usage in LCTFs was performed by the European Surveillance of Antimicrobial Consumption (ESAC), and this included 323 LCTFs distributed across the territories of all EU countries. The main prevalence rate of antibiotic prescribing calculated was 6.3% range 1–17.3%) . Then, i.3% . TheItaly also participated in the aforementioned HALT-2 and HALT3; the antibiotic usage found was 4% and 3.9%, respectively, higher than the prevalence rate registered in our study.Nevertheless, the findings that emerged here are not entirely comparable due to the several typologies of LCTFs included in the other studies. To analyze the phenomenon in a homogenous sample and reduce the risk of selection bias, we decided to exclude LCTFs with mixed populations. Indeed, we included only LCTFs that deliver residential care to elderly people (>65 years) unable to live independently and requiring assistance in daily living activities. In addition, discrepancies in comparing all those surveys could be partially justified by the different data collection times. We decided to perform our cross-sectional survey at the end of February, when the peak of flu was overcome, in order to reduce the risk of a potential bias.Residents included in our study do not differ significantly compared with previous European surveys ,17.We found a median age of 84.36 among patients in treatment with antibiotics, in line with other similar studies conducted in Slovenia (median age 83.5) and the rest of Europe (median age 85) . In suppMost of the antibiotic users included in our analysis were male, in line with a previous cross-sectional Canadian survey . Indeed,By contrast, the Finnish and Swiss studies previously mentioned showed a specific influence of the female sex on the prevalence of the consumption of antibiotics ,29. The Forty-eight percent of our patients on antibiotic treatment were diagnosed with dementia. Nevertheless, unlike the Slovenian study, we did not find a higher prevalence of dementia diagnosis among patients on antimicrobial treatment . ConversIn accordance with the Finnish study, we also found a positive association between being immobilized and higher usage of antibiotics .The most prescribed antibiotics were amoxicillin plus clavulanate and macrolides, partially in line with European data.Amoxicillin and clavulanate were prescribed more frequently than the other penicillins.In addition, a worrying concern is the high usage of fluoroquinolones, which, similar to amoxicillin, is listed among the broad-spectrum antibiotics responsible for antibiotic resistance .Among patients on treatment with antibiotics, only 12% received them for prophylaxis, which is lower than in other European studies. HALT2 and HALT3 registered remarkable prophylactic usage of antimicrobial drugs (respectively 27.7 and 27.2). The prevalence of residents on treatment with antimicrobial agents for prophylaxis varies across countries. The aforementioned Slovenian point prevalence survey demonstrated recourse to prophylaxis for only 1.2% of enrolled residents . By contThe aim of this investigation was not to assess the appropriateness of antibiotic prescribing and usage in LCTFs in Novara LHA. A recently published survey conducted in the Netherlands demonstrated that improvements in appropriateness might result in a drastic and significant reduction in antibiotic prescription prevalence . HoweverLastly, we found frequent usage of azithromycin in patients with COVID-19. Azithromycin is listed among the broad-spectrum antimicrobial agents with good absorption after oral intake and powered by a long half-life . GeneralThis study presents some limitations that must be taken into account. Firstly, this study was carried out only on the population of the Novara LHA, which represents a small part of the Italian population. Indeed, our results may not be entirely generalizable to the entire nation. Secondly, data collected are part of a point prevalence study, and, due to this, they offered only a photograph at that point in time.Another limitation of this survey was its cross-sectional design; a survey, especially if administered on only 1 day, could be potentially subjected to several variations. Nevertheless, we decided to adopt this methodological approach because of its feasibility when applied to settings characterized by limited human resources in terms of the workforce, such as LCTFs, especially during the COVID-19 pandemic.On the other hand, among the strengths of our study, it is possible to cite the use of a standardized survey across all participating LCTFs, the collection of detailed data on LCTF characteristics, and the use, when necessary, of administrative health databases.A broad number of LCTFs responded to our invitation, so the large sample size of the population included provides a detailed picture of antimicrobial consumption in LCTFs. In addition, the baseline demographic and clinical characteristics of the included population, similar to several studies from European countries, suggest that our data are not influenced by potential selection bias and offer a realistic photograph.Our results might represent a useful tool to better understand the potential determinants and the magnitude of this issue and to inform local and national public health policymakers on the importance of the prudent prescription of antimicrobial agents.Similar routine surveillance studies are warranted to identify trends and changes in pathogen incidence and antimicrobial resistance, including new pathogens at local, national, and global levels.Periodic monitoring of antibiotic consumption through standardized systems in line with national and European legislation is also needed to build and clarify approaches aimed at controlling antimicrobial resistance, guiding clinicians’ and policymakers’ decisions on the appropriate use of antibiotics and on the need for adopting and incorporating guidelines available on this theme in LCTF protocols.