Antibiotic resistance (ABR) and antimicrobial stewardship arethe two sides of the same coin that constitute a public health hydra. This study aimed to assessthe knowledge and attitude of healthcare workers (HCWs), on antibiotic use and antimicrobial resistance in Western Greece. A total of 200 healthcare workers  from the two largest tertiary hospitals in Western Greece were included in our survey. HCWs seem not to decide based on patient opinion in order to prescribe antibiotics. Approximately 97% of them are aware of their main adverse effects. Remarkably, 25% of respondents prescribe antibiotics due to diagnostic uncertainty, and 32.5% of them prescribe antibiotics based on their experience. HCWs statedthat they do not report adverse effects often. Inappropriate antibiotic prescriptions were mentioned as the main reason for bacterial resistance to antimicrobials. Monitoring the patient’s treatment progress, using electronic prescriptions, and adhering to international guidelines were suggested as solutions to the problem. Post Hoc analysis showed that nursing staff apply to the national guidelines (p: 0.011) and use electronic prescriptions (p: 0.003) less often compared to consultants, doctor directors, and trainees. The findings of our survey may be useful for the development of future national education programs and interventions thatmay improve healthcare workers’ knowledge and ability to manage antibiotics. Antibiotics’ rampant use and inappropriate prescriptions lead to antimicrobial resistance. According to WHO, 20–50% of the antibiotics distributed to primary care are misused . At presGreece has one of the highest rates of antibiotic consumption and resistance among European countries. The link between antimicrobial consumption and resistance is well-known . Even thThe implementation of measures to restrict the use of certain antibiotics has been proven to reduce inappropriate antimicrobial administration. Following the introduction of electronic prescribing and Antibiotic Hardstop, a significant reduction has been observed in the days of therapy and length of therapy for antimicrobial use without a significant increase in adverse events .The aim of the present study was to assess the knowledge and attitude of healthcare workers (HCWs), regarding antibiotic use, side effects, overprescription, and consequently antimicrobial resistance. The results of this study may help identify those HCWs with knowledge gaps and assist in the design of future educational interventions that will enable more rational antimicrobial prescribing.This is a cross-sectional observational study that was conducted in the two largest tertiary hospitals in Western Greece, based on a scripted questionnaire. The questionnaire was randomly distributed to healthcare workers, including residents, consultants, nurses, technicians, and others. Healthcare workers were invited to participate in our survey during a period of 3 months (May to July 2023).An overview of this study objectives was provided to potential participants.The questionnaire was pre-developed by independent members of our research team based on pertinent current literature ,9,10. InThe questionnaire was written in Greek and consisted of three parts. Part A included six questions regarding demographic characteristics . Part B included five questions regarding knowledge of antibiotic use . Part C included seven questions regarding knowledge and attitude towards antibiotic resistance.This study was conducted in line with the Ethics Committee of our University , the guidelines of the Declaration of Helsinki, and STROBE guidelines.Statistical analysis was conducted using IBM SPSS Statistics, version 28. The level of significance was set to 0.05. Descriptive statistics were used to summarize all the data on demographic characteristics, knowledge, and attitudes regarding antibiotics, antibiotics’ use, and resistance. Post Hoc analysis was used to determine any statistically significant difference between the parameters compared. Comparisons between pairs of groups were performed using the simplest post hoc analysis, the Bonferroni test.A total of 200questionnaires, out of 520 randomly administered, were answered and included in this study (response rate: 38.5%). Among the respondents, 74.5% (n = 149) were females and 25.5% (n = 51) were males. Socio-demographic and professional characteristics  of the participants are presented in General knowledge regarding antibiotic use was confirmed in many questions . In terms of antibiotics’ use, most of the participants (32.5%) answered that they often prescribe antibiotic regimens based on their experience and 25% due to diagnostic uncertainty. Patients’ requests for involvement in HCWs decisions to prescribe antibiotics are shown in Almost all participants were aware of common antimicrobial regimen side effects, including gastrointestinal tract symptoms and allergic reactions, as shown in Curiously, several participants stated that they have never reported antibiotic side effects due to an extensive workload , or even because they degraded them . Another frequent reason was the lack of knowledge regarding the obligation to declare adverse side effects . Moreover, post hoc analysis showed that trainees had statistically significantly less knowledge and skills to recognize adverse reactions after the administration of antibiotics compared to consultants and directors (p = 0.001).Almost all of the participants (97%) stated that antibiotic resistance is a serious public health issue in Greece. .The most frequent explanation (64.5%) for increased antimicrobial resistance in Greece was that antibiotics are used inappropriately by HCWs. Overprescription (61.5 %), and over-the-counter consumption (55.5%) were two other frequent explanations .In order to mitigate the consequences of rampant use of antibiotics, HCWs responded that they try to adhere to local guidelines, use e-prescription, conform to current evidence, and track patients to observe their outcomes .Post Hoc analysis showed that nursing staff have less adherence to guidelines compared to consultants, directors, and trainees (p = 0.011).The use of electronic prescription systems among doctors has strong statistical significance compared to nursing stuff (p: 0.003). No statistically significant differences were found regarding continuing education and monitoring of patients care  between nurses and doctors .Antibiotic resistance and antibiotic stewardship are crucial factors that undermine the quality of healthcare systems. This is the first study in Western Greece that underlines the urge for proper HCWs education and strict application of rules and guidelines.Our survey investigated healthcare workers’ knowledge of antibiotic use and antibiotic resistance, as HCWs are the key stakeholders in the prevention and control of antibiotic resistance. Apparently, HCWs knowledge of antimicrobial regimens’ mechanisms of action and resistance mechanisms would prevent further increases in antimicrobial resistance . This stUnfortunately, 32.5% of the participants answered that they often prescribe antibiotic treatment based on their experience and 25% due to diagnostic uncertainty. Similarly, Christensen I. et al. reported that even in Norway, where antimicrobial resistance rates are among the lowest in Europe, one of the main reasons physicians prescribed antibiotics was clinical uncertainty . MoreoveThis study showed poor knowledge and practice regarding antibiotic use. Most participants answered that they inform their director about side effects related to antibiotics’ use instead of writing the appropriate yellow card. This is due to a lack of both knowledge and experience. Such findings reflect the lack of efficacious educational programs. HCWs, especially nurses and trainees, need to extend their knowledge regarding antibiotic use . With alNurses dramatize a crucial role in efforts to address this worldwide public health problem. Although in Greece nurses do not prescribe antibiotics, this study aims to evaluate their knowledge regarding national guidelines and the electronic prescription system. As anticipated, nurses performed insufficiently on practices related to antibiotic use . These findings are in line with a study by Farley et al., which revealed disparity among nurses concerning the awareness and understanding of optimal antibiotic prescribing practices . HoweverAlmost all the participants (97%) in the current study agreed with the statement that antimicrobial resistance is a significant public health issue in Greece. Similarly, Firouzabadi et al. and Mahmoudi et al. reported that antimicrobial resistance was considered a crucial problem by 73.8% of the participants . RemarkaAs most of the participants mentioned unrestricted prescription and administration of antibiotics as the main contributing factors to antimicrobial resistance, 46% of them agreed that monitoring patients’ treatment progress can reduce antibiotic resistance. Further, 43% of them agreed that the use of electronic prescriptions can reduce antibiotic resistance. Cotta MO et al. data were inconsistent with our findings, demonstrating that limiting antibiotic prescription by an approval process, such as electronic prescribing, was the least approved intervention . FinallyOur study, as a real-world study, has some limitations. At first, it was a two-center study with a small number of participants. Secondly, participation in our study was voluntary; therefore, HCWs feeling uncomfortable may have deliberately decided not to participate, causing selection bias. Another limitation is that participants may give desirable answers rather than their actual beliefs. For those reasons, we cannot generalize these findings.However, the main strength of our study is that we included qualitative parameters, which helped us explore the ideas prevalent among this study population that would not have been revealed in a quantitative study.In our study, a knowledge deficit was observed in some aspects of antimicrobial use. The findings of our survey may be useful for the development of future educational programs and interventions that focus specifically on promoting behaviors that lead to prudent prescription, dispensing, and administration of antibiotics. Furthermore, they highlight the need to continue to raise awareness about appropriate and correct use of antibiotics and antibiotic resistance and to enhance healthcare workers’ engagement in addressing these issues. Finally, coordinated efforts to implement new policies, renew research efforts, and pursue steps to manage the crisis are greatly needed.


According to CDC (2019), antibiotic-resistant infections affect more than 2 million people. By 2030, 100 million people will die prematurely as a result of uncontrolled antibiotic use, and in 35 years, this figure will reach 300 million . Despite of modern patient target approach to curing majority of diseases, the problem of antibiotics over usage is still urgent in middle-income countries due to non-profile prescription, absence of microbiological confirmation and the ease of availability of antibiotics.To investigate antibiotic usage expedience for a 1-year duration among Ukrainian and foreign medical students.A total of 150  medical students were examined by questionnaire for antibiotic usage during last year with specification of reasons, course frequency and duration, expediency of appointment, treatment outcomes, possible reason for cancellation/replacement of antibiotic therapy and preventable usage cases.n = 49)] and 33.8% (n = 25) Ukrainians used antibiotics for different reasons during February 2022–January 2023 (P < 0.01). Antibiotic usage by physician’s prescription was held among 24.49% (n = 12) foreign students and 68.18% (n = 12) Ukrainian ones (P < 0.05). The frequency of antibiotic application due to positive result of bacteriological investigation was significantly lower among foreign responders: 27.27% versus 4.00% in Ukrainians (P < 0.05). In the Ukrainian students sample 36.3% (n = 8) responders predisposed to antibiotic usage for infectious condition appearance . The frequency of ≥3 antibiotic courses per year prevailed in the foreign student group . The analysis of post-antibiotic adverse events found out allergic reaction in 1.2% (n = 1) in the foreign sample, diarrhoea 1.56% (n = 1) and change of antibiotic due to ineffectiveness 1.56% (n = 1) in the Ukrainian sample.The majority of foreigners [60.5% (Possible predictors of the formation of resistance to antibiotics among young people living in developing countries, such as incorrect clinical use, lack of control over the prescription of antibiotics, ease of availability of antibiotics and as a result of self-medication, were evaluated. The prophylactic prescription of broad-spectrum antibiotics for routine procedures, such as preparation for surgical interventions and in the postoperative period, also draws attention.


Similarly, the recommendation for aspiration thrombectomy (AT) is downgraded to very selective use. We examine the prevalence, and predictors of GPI and AT use in STEMI patients referred to primary percutaneous coronary intervention (PCI). Data on 116,873 consecutive STEMI patients referred to primary PCI in Poland between 2015 and 2020 were analyzed. GPIs were administered in 29.3%, AT was used in 11.6%, and combined treatment with both in 6.1%. There was a mild trend toward a decrease in GPI and AT usage during the analyzed years. On the contrary, there was a rapid growth of the ticagrelor/prasugrel usage rate from 6.5 to 48.1%. Occluded infarct-related artery at baseline and no-reflow during PCI were the strongest predictors of GPI administration  and combined usage of GPI and AT  in a multivariate logistic regression model. Similarly, the administration of ticagrelor/prasugrel was an independent predictor of both adjunctive treatment strategies. In STEMI patients in Poland, GPIs are selectively used in one in four patients during primary PCI, and the combined usage of GPI and AT is marginal. Despite the rapid growth in potent P2Y12 inhibitors usage in recent years, GPIs are selectively used at a stable rate during PCI in highly thrombotic lesions.In the era of potent P2YThe online version contains supplementary material available at 10.1007/s11239-023-02811-z. GPIs and aspiration thrombectomy are selectively used in contemporary STEMI patients during primary PCI in Poland, with GPIs administered in one in four patients and aspiration thrombectomy in one in ten patients.The rapid growth in the use of potent P2Y12 inhibitors, such as ticagrelor and prasugrel, in Poland has not led to a significant reduction in the use of GPIs and aspiration thrombectomy during primary PCI in STEMI patients.The target population for GPI administration and/or aspiration thrombectomy during primary PCI in STEMI is characterized by a higher ischemic risk profile, indicating that these strategies are being used selectively in patients with a greater need for aggressive treatment.12 inhibitors, ticagrelor and prasugrel, the role of GPIs remains discussed due to unclear benefits and safety of such combined therapy [12 inhibitor was not administered before PCI [12 inhibitors may be delayed in STEMI patients, especially in those with hemodynamic instability or concomitant opioid administration [Rapid platelet inhibition is a crucial part of reperfusion therapy with primary percutaneous coronary interventions (PCI) in patients with ST-elevation myocardial infarction (STEMI). Glycoprotein IIb/IIIa inhibitors (GPIs) were routinely used as adjunctive periprocedural pharmacotherapy in the era of clopidogrel , 2. Afte therapy , 4. Acco therapy . GPIs cafore PCI . Similarfore PCI . On the stration , 8. ThesPresented study aimed to examine the prevalence, procedural characteristics, and predictors of GPI administration in all-comers contemporary STEMI patients referred to primary PCI in Poland. Considering the procedural approach to thrombus-containing lesions we also analyzed data on the combined usage of GPIs and aspiration thrombectomy.12 inhibitors and "bridging" therapy in patients in which a P2Y12 inhibitor was not administered before PCI. Angiography was assessed by PCI operators but not by the core-lab. We focused on two strategies during procedures: (1) GPIs administration and (2) the combined usage of GPIs and aspiration thrombectomy. Results were also analyzed in the context of potent P2Y12 inhibitors periprocedural treatment . Additionally, we analyzed the usage of both treatment strategies according to site STEMI volume.The presented analysis focused on consecutive STEMI patients referred to Primary PCI in Poland between 2015 and 2020. Data were prospectively collected and stored via electronic case report forms in the National PCI Registry (ORPKI) operated by the Jagiellonian University Medical College in Krakow and endorsed by the Polish Association of Cardiovascular Interventions of the Polish Cardiac Society. ORPKI is a national registry collecting data on all PCI procedures performed in Poland –11. For Standard descriptive statistics were used in the analysis. Quantitative variables were described with median with interquartile range . Normality was assessed by the Shapiro–Wilk test. Categorical variables were presented as percentages. Chi square test or Fisher Exact Test were used for comparing categorical data, as appropriate. Temporal trends were analyzed with Cochran-Armitage trend test. A logistic regression analysis was constructed to identify predictors of the use of GPIs and aspiration thrombectomy. Variables, including demography, clinical characteristics, and angiography parameters, were considered by calculating simple models. Final multiple models were constructed using a stepwise combined (forward/backward) technique with minimization of the Bayesian Information Criterion as a target, taking into account all variables with p-value from simple model < 0.2 or of clinical importance. Results are presented as odds ratios with an associated 95% confidence interval. The level of statistical significance was set at alpha value < 0.05. All statistical analyses were performed using the R version 4.1.1  with package “rms” version 6.2–0 and JMP 15.2 .During six years, 116,873 consecutive patients in STEMI were treated with primary PCI. GPIs were administered in 29.3% of these patients , aspiration thrombectomy was used in 11.6%, and combined treatment with GPIs and aspiration thrombectomy in 6.1%. There was a trend towards decrease in GPIs and aspiration thrombectomy usage during the analyzed years, which was mainly seen between 2015 to 2018 with a plateau beyond 2018 at the level of about 27% for GPIs and about 10% for aspiration thrombectomy. Conversely, there was rapid growth in ticagrelor/prasugrel usage rate from 6.5% in 2015 to 48.1% in 2020 . In angiography, we observed a higher rate of the occluded infarct-related artery in baseline angiography (more often the right coronary artery) and a higher rate of no-reflow during PCI. They more often received ticagrelor/prasugrel (Table S2 in supplementary information).Similarly to GPIs administration analysis, the occluded infarct-related artery at baseline and no-reflow during PCI were the strongest independent predictors of combined usage of GP IIb/IIIa inhibitors and aspiration thrombectomy in a multivariate logistic regression model. Results of univariate and multivariate logistic regression analysis are presented in table S3 in supplementary information.We analyzed the usage of both treatment strategies (rate of GPIs administration and combined treatment with of GPIs and aspiration thrombectomy) according to site STEMI volume (quartiles). Data according to site volume (primary PCI in STEMI) quartiles are presented in Fig. The most important findings from the presented analysis are: (1) in all-comers contemporary STEMI patients in Poland, GPIs and aspiration thrombectomy are selectively used in respectively one in four and one in ten patients during primary PCI in STEMI, (2) the combined treatment strategy with both GPIs and aspiration thrombectomy during primary PCI is marginal, (3) the use of those strategies was not particularly reduced by the rapid growth in potent P2Y12 inhibitors use in Poland in recent years, (4) target STEMI population for GPI administration is characterized by high ischemic risk.12 inhibitors, ticagrelor and prasugrel, the role of GPIs is debatable mainly due to the lack of clear data on the benefits and bleedings risks of such an approach. According to current guidelines, their usage should be limited to bail-out and/or highly thrombotic situations [12 inhibitors. Over, the results of our analysis do not fully confirm these assumptions, as we observed only a mild trend towards decrease in use of GPIs through years 2015–2020, despite the pronounced increase in use of ticagrelor and prasugrel. Blanchart K et al. showed (based on prospective registry data) the GPI usage in 41% of STEMI patients treated with ticagrelor or prasugrel during primary PCI. Importantly, 52% of those patients have received GPI as a systematic strategy [12 inhibitors is elevated bleeding risk. However, to date, there is no dedicated clinical trial to assess such risk  in the contemporary STEMI cohort. In the above-mentioned registry with the 98% of radial approach there was no significant increase of bleeding in the GPI cohort [12 inhibitors compared to GPI and clopidogrel. The increase in bleeding risk with GPIs was present regardless of the type of P2Y12 inhibitor but relative risk was higher with clopidogrel than with ticagrelor or prasugrel. This suggests that GPIs treatment is the main factor of elevated bleeding risk, and administration of potent P2Y12 inhibitors may have no further influence on bleeding risk [12 inhibitors compared to clopidogrel in reducing the risk of ischemic events is independent of GPI use [12 inhibitors. [12 inhibitor, GPIs were administered in about one third what is slightly lower rate comparing to other studies [Primary PCI of thrombotic lesions in patients with STEMI may be challenging due to the risk of no-reflow and distal embolization. Rapid platelet inhibition plays an important role during mechanical reperfusion , 13. GPItuations . These mstrategy . Similarstrategy . The maiI cohort . Meta-aning risk . On the  GPI use . This unibitors. . In our  studies , 17.Aspiration thrombectomy is a tool designed for mechanical thrombus removal and to prevent distal embolization . In initThe presented study has several limitations. First, the observation is limited only to procedure time, and no longer follow-up was available. Analysis is based on registry data describing everyday clinical practice; thus, it is impossible to compare the outcomes of different strategies with GPIs and aspiration thrombectomy due to important differences in baseline characteristics. Because of the two above-mentioned limitations, there is no point in performing further statistical analysis for in-cathlab outcomes, even including propensity score matching. Data about the way of bolus administration (intravenous or intracoronary) and infusion details are unavailable. However, routine practice is to give infusion after bolus injection. Finally, angiograms were assessed by operators. No core lab analysis was performed in this registry.The presented analysis shows that GPIs are used in primary PCI in STEMI in one in four patients in Poland, and combined use of GPIs and aspiration thrombectomy is marginal. An increase in ticagrelor and prasugrel use does not seem to impact rates of use of GPIs and thrombectomy in Poland. The target population for GPI and/or thrombectomy is characterized by high ischemic risk.Supplementary file1 (DOCX 24 kb)Below is the link to the electronic supplementary material.


Background: Inappropriate antibiotic use for community-acquired pneumonia (CAP) is common. Although antibiotic stewardship activities require real-time, accurate identification of patients being treated for CAP, there are few reliable methods to identify such patients using the electronic health record (EHR). We conducted a retrospective study to assess the performance of provider-selected antibiotic indication in identifying patients being treated for CAP among a cohort of hospitalized adults. Methods: We randomly selected 440 patients from a cohort of patients who received at least 1 systemic antibiotic within 48 hours of admission between January 1, 2019, and December 31, 2021, at 3 acute-care hospitals. The reference standard for treatment of CAP was defined as intention to treat for pneumonia by inpatient provider(s) within 48 hours of admission, as assessed by chart review of provider notes. Treatment for pneumonia using any terminology except with “hospital-acquired pneumonia” (HAP) or “ventilator-associated pneumonia” (VAP) were counted. Provider-selected indication of CAP (in an antibiotic order) was compared against this reference standard; sensitivity, specificity, and positive and negative predictive values were calculated. Performance characteristics of International Classification of Disease, Tenth Revision (ICD-10) codes for pneumonia in identifying CAP patients were assessed against the same reference standard. A secondary analysis including terms HAP and VAP in the reference standard was performed. Results: Provider-selected antibiotic indication for CAP had a sensitivity of 64.4%, specificity of 96.3%, positive predictive value (PPV) of 73.1%, and negative predictive value (NPV) of 96.1%, giving comparable performance to ICD-10 codes (Table 1). Of those with 21 false-negative results, 13 (61.9%) had a healthcare-associated lower respiratory tract infection and 14 (66.7%) had sepsis indicated in at least 1 antibiotic order. Conclusions: Provider-selected antibiotic indication showed moderate sensitivity and high specificity for identifying CAP-treated cases. Importantly, use of this method can be deployed for real-time antibiotic stewardship interventions for CAP.Disclosures: None


To evaluate antibiotic prescribing behavior (APB) among physicians with various specialties in five Asian countries.Survey of antibiotics prescribing behavior in three stages .Participants included internists, infectious diseases (ID) specialists, hematologists, intensivists, and surgeons. Participants’ characteristics, patterns of APB, and perceptions of antimicrobial stewardship were collected. A multivariate analysis was conducted to evaluate factors associated with appropriate APB.There were 367 participants. The survey response rate was 82.5% (367/445). For the initial stage, different specialties had different choices for empiric treatment. For the on-treatment stage, if the patient does not respond to empiric treatment, most respondents will step up to broader-spectrum antibiotics (273/367: 74.39%). For the de-escalation stage, the rate of de-escalation was 10%–60% depending on the specialty. Most respondents would de-escalate antibiotics based on guidelines (250/367: 68.12%). De-escalation was mostly reported by ID specialists (66/106: 62.26%). Respondents who reported that they performed laboratory investigations prior to empirical antibiotic prescriptions (aOR = 2.83) were associated with appropriate use, while respondents who reported ID consultation were associated with appropriate antibiotic management for infections not responding to empiric treatment (aOR = 40.87); adherence with national guidelines (aOR = 2.57) was associated with reported successful carbapenem de-escalation.This study highlights the variation in practices and gaps in appropriate APB on three stages of antibiotic prescription among different specialties. Education on appropriate investigation, partnership with ID specialist, and availability and adherence with national guidelines are critical to help guide appropriate APB among different specialties. According to Centers for Disease Control and Prevention (CDC), an estimated 50% of antibiotics prescribed in the Unites States is inappropriate. Antibiotic prescriptions are divided into three stages . At the initial stage, physicians often use broad-spectrum antibiotics, even in nonbacterial infections without appropriate investigations. During the on-treatment stage, physicians may not perform appropriate diagnostic tests  or may not adjust antibiotics according to microbiological culture results. Additionally, during the de-escalation stage, a physician may not recognize the need for de-escalation or discontinuation of antibiotics. Integration of behavior theory to evaluate antibiotic prescribing behaviors (APB) is needed. A previous study suggested that transtheoretical model (TTM) of health behavior change can be used to evaluate APB among physicians. Physicians who are in higher stages of TTM are assumed to exhibit appropriate APB.Inappropriate antibiotic prescriptions lead to the selection of drug-resistant organisms, Internists, hematologists, and intensivists often prescribe broad-spectrum antibiotics in febrile neutropenia or in critically ill patients when not indicated, while surgeons prescribe multiple courses of antibiotics and escalate empiric treatment when not indicated. To limit unnecessary antibiotic prescriptions, it is important to understand APB among physicians in various specialties. This information will help inform appropriate intervention to improve appropriate APB for various specialties. We therefore performed a multinational survey to evaluate APB among physicians in various specialties and factors predicting appropriate APB in each stage.It is well recognized that physicians from various specialties have different APB.The survey was conducted in five countries . Participants of each specialty  specialist, hematologist, intensivist, and surgeon) were invited to participate in the survey based on a convenience sample. Prior to the survey, the questionnaire was assessed by all investigators to verify that it covered the information needed to achieve the study goals. The survey was performed from November 1 to December 31, 2022. Google forms were created and distributed through texts (LINE application) or email. Institutional ethical committee approval was obtained prior to the conduct of this survey. TTM stage was categorized into five stages: precontemplation, contemplation, preparation, action, and maintenance. Precontemplation is the first stage in which people do not intend to change their behavior in the upcoming future. The next stage is contemplation; people are starting to be aware of the situation and consider changing their actions. Preparation is the stage in which people decide to act in the near future. Action is the stage in which people begin to change their behavior. The last stage is maintenance (MT); at this stage, the behavior has changed and people are trying to maintain it. In the on-treatment stage, respondents were asked to select their investigations and management in two situations; if their patient’s condition is getting worse and if the organism identified is a multidrug-resistant organism. Lastly, in the de-escalation stage, respondents were asked to choose factors that influence antibiotic de-escalation, frequency of antibiotic de-escalation, and their experience in successful carbapenem de-escalation.Information collected included age, gender, specialty, level of training, country, total number of beds of the hospital where the participant primarily practiced, availability of ID consultants, and patterns of APB among various specialties. The survey collected data on patterns of antibiotic use, perceptions on the practice of antimicrobial stewardship, adherence to national prescribing guidelines, and analysis of factors associated with prescribing behaviors. It was divided into three stages . In the initial stage, respondents ranked the top three most common indications for antibiotic prescriptions, chose routine investigations prior to prescribing antibiotics, selected typical empiric antibiotics, reported on influences on prescribing antibiotics, and their antibiotic behavior based on the five stages from the TTM. For the on-treatment stage, appropriate management for infections not responding to empiric treatment was defined as appropriate investigations . For the de-escalation stage, successful carbapenem de-escalation was defined as reporting successful carbapenem de-escalation more than 80% in their clinical practice.Definitions of appropriate antibiotic prescriptions for each stage were defined as follows. First, in the initial stage, appropriate empirical antibiotics were defined as the administration of proper empirical antibiotics based on the local antibiogram and the adopted institutional guideline for each specific indication.2 tests were used to compare categorical variables. Independent t-tests were used for continuous data. All P values were two-tailed, and P < .05 was considered statistically significant. A multivariate analysis was conducted to evaluate factors associated with certain APB in various specialties in three stages. Adjusted odd ratios (aORs) and 95% confidence intervals (CIs) were calculated.All analyses were performed using SPSS, version 26 . χOverall, 367 physicians from five countries participated in the survey. The overall survey response rate was 82.47% (367/445). The response rates (responded/invited) were from Thailand , Korea , Singapore , Japan , and Hong Kong . The proportions of each participant were from Thailand , Korea , Japan , Singapore , and Hong Kong . The middle age range of participants was 31–40 years. The majority of participants were male . Most participants were staff (235/367: 64.03%) and were from the department of infectious diseases (106/367: 28.88%), internal medicine (91/367: 24.80%), and surgery (64/367: 17.44%). Almost all had ID consultants available at their respective hospitals . For the behavioral assessment of prescribing practice, most physicians were categorized in the MT stage of TTM . Characteristics of the study population and APB are summarized in Table P = .197]. The use of biomarkers/rapid diagnostic tests (RDTs) inclusive of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and procalcitonin to help with empiric antibiotic choices were more commonly reported in the initial stage  compared to on-treatment  and de-escalation stage .For the initial stage, sepsis workup, including blood cultures, urine cultures, and sputum cultures, was the most common routine investigation performed prior to prescribing antibiotics . Most physicians prescribed a β-lactam/β-lactamase inhibitor as their empiric antibiotic  and were mostly influenced by international guidelines for treatment of organ-specific infections . Different specialties have different patterns of empirical antibiotic use  and will repeat the sepsis workup (286/367: 77.93%) together with multi drug resistance testing  to further identify the pathogens as well as their susceptibility profile. The patterns of workups and management of infections not responding empiric treatment among various specialists are summarized in Table P < .001). Successful de-escalation experiences were reported by 61%–80% among internists and ID specialists and 41%–60% among hematologists, intensivists, and surgeons. Notably, most physicians who adhered with national prescribing guidelines were more likely to have reported successful carbapenem de-escalation . Compared to the non-MT stages, participants who were classified in the MT stage were more likely to prescribe appropriate antibiotics in the de-escalation stage . Characteristics and patterns of APB among various specialties in the three stages are summarized in Table For the de-escalation stage, the majority of participants reported de-escalating antibiotic regimens based on guidelines for the treatment of organ-specific infections . De-escalation was mostly reported by ID specialists  and internists , while other specialists reported de-escalation much less frequently  while being a trainee  and prescribing antibiotics based on a role model (as opposed to guidelines)  were associated with reported inappropriate empiric antibiotic prescriptions. For the on-treatment stage, behaviors associated with appropriate management infections not responding to therapy included consulting ID  and practicing medicine in Japan , while continuing the same antibiotics without investigation  was associated with reporting inappropriate treatment in the on-treatment stage. For the de-escalation stage, behaviors associated with successful carbapenem de-escalation included practicing medicine in Japan  and compliance with national prescribing guidelines , while practicing as intensivists  and hematologists  was associated with reported failure to de-escalate carbapenem therapy. Factors associated with appropriate antibiotic prescriptions in the three stages are summarized in Table There are several notable findings in our study. First, APB varied based on specialties, inclusive of investigations prior to antibiotic administration in both the initial and on-treatment stages, the pattern of antibiotic prescription, and further management of patients with infections not responding to therapy. Notably, the use of biomarkers was more commonly reported in the initial stage, while participants who were in the MT stage of TTM were more likely to prescribe appropriate antibiotics in the de-escalation stage. Second, adequate investigation, inclusive of source control during the on-treatment stage, was only reported by ID specialists. Third, antibiotic de-escalation was commonly reported only by ID specialists, while successful carbapenem de-escalation was reported by 41%–80% of respondents as categorized by specialty. To the best of our knowledge, this study is the first to explore APB among different specialties by a multinational survey in Asia. This knowledge will help identify the gap of antibiotic administration in different stages to help promote appropriate antibiotic prescriptions among physicians in different specialties. Further investigation should be conducted to determine why Japanese physicians are much more accepting of the concept of de-escalation of empiric therapy compared to other Asian nationalities. While broad-spectrum antibiotics are usually prescribed for empiric treatment among internists, the use of narrow spectrum antibiotics followed by escalation to broader-spectrum antibiotics are usually observed among surgeons. Additionally, several studies found that incorrect antibiotic dosing and inappropriate use of broad-spectrum antibiotics such as carbapenems and vancomycin are common practices in treating patients with febrile neutropenia and those in critical care settings. Similarly, our study found that the patterns of empiric antibiotic prescription among specialties can differ based on common sites of infections as well as the adopted international guidelines in each country. Inappropriate APB was commonly reported by trainees, and these young physicians were influenced by their role models suggesting the importance education in younger groups of physicians in all specialties. Several guidelines and consensus suggest the benefit of RDTs and biomarkers, including procalcitonin to help reduce inappropriate antibiotic use during the initial, on-treatment, and de-escalation/cessation stage. These RDTs and biomarkers can be integrated in antibiotic stewardship to improve the diagnostic and therapeutic management for various indications, including acute respiratory infections and sepsis. However, our study found that use of these RDTs and biomarkers was limited to procalcitonin and mostly only used in the initial stage. It is therefore imperative that more education is provided for the appropriate use of RDTs and biomarkers in all stages.APB, including the choice of empiric antibiotics and the use of biomarkers to help with empirical in the initial stage, can vary by specialty. Failure to respond to antibiotic therapy may occur due to a miss diagnosis, an infectious complication, or the lack of source control. Our study found that only ID specialists consistently consider source control, while other specialties chose to step up to broader-spectrum antibiotics with/without appropriate investigations. Several studies have shown the benefit of ID consultation to assist with appropriate investigation and antibiotics administration in different clinical sites. ID consultation may include recommending the appropriate choice of antibiotics and reducing the use of broad-spectrum antibiotics, which result in the reduction in antibiotic expenditure as well as improved clinical outcomes. Likewise, we found that ID consultation was associated with appropriate management for patients who fail to respond during the on-treatment stage. National antibiotic guidelines and policies have been shown to increase awareness of the harm of over prescription of antibiotics and reduce the inappropriate use of antibiotics. In Japan, implementation a national antibiotic policy was associated with reducing in total antibiotics use. Our data emphasize the important role of the implementation of national guidelines to help with appropriate management of antibiotics during the on-treatment stage.During the on-treatment stage, adding or switching to broader-spectrum antibiotics is the most common practice if the patients fail to respond to antibiotics therapy. Predictors for antibiotic de-escalation include positive microbiological culture results, consultation with an ID specialist, and adherence to national guidelines. Carbapenem de-escalation has been reported to be 45%–50% by several studies. In our study, the rate of de-escalation was reported to be 10%–60% depending on the specialty. Notably, de-escalation was less commonly reported by hematologists and intensivists, and this may be due to the severity of illness among their patient population. Adherence to national prescribing guidelines has been shown to help with carbapenem de-escalation. Likewise, our study found that adherence to national prescribing guidelines is associated with appropriate de-escalation. In addition, several studies have reported on the use of behavioral theories to evaluate APB. A Thai study showed a strong correlation between the TTM stages and appropriate antibiotic prescriptions in surgical wards during the initial stage. Likewise, our study found that participants who are in the MT stage were more likely to report appropriate APB in the de-escalation stage. Therefore, it is important to provide more education on the appropriate use of APB among participants who belong to the earlier TTM stages during de-escalation.Antibiotic de-escalation has been shown to reduce the risk of antimicrobial resistance and adverse effects from unnecessary antibiotic use.Our study had several limitations. First, the nature of a self-reported survey lends to a situation in which the actual practice may not reflect what participants report. However, we were very clear to potential participants that the survey is de-identified and completely anonymous and so the reported behavior is more reflective of the practice. Second, the nature of a convenience sample survey may be subject to selection biases. Third, as the majority of the participants were staff, being internists and ID specialists, and were from Korea, Thailand, and Japan, it is possible that our results may skew toward the practices in these specialties and countries. Lastly, the small sample size may limit our ability to identify other factors associated with APB in the initial, on-treatment, and de-escalation stages.In conclusion, this study shows that there are differences in APB in the initial, on-treatment, and de-escalation stages among different specialties. These differences in behaviors can be reduced by educating prescribers on the use of RDTs and biomarkers during the initial stage, consulting ID specialists during the on-treatment stage, and increased adherence to national antibiotic prescribing guidelines during the de-escalation stage.


Antibiotic use and resistance in animal production are a concern to public health, and there is an urgent need to reduce antibiotic use in farm animals. To prevent blame shifting, professionals from human medicine, animal medicine and environmental backgrounds must collaborate to tackle this issue. Veterinarians are typically responsible for overseeing and prescribing antibiotic use in animals. There are currently no available studies on the opinions of Irish farm animal veterinarians on antibiotic use, reduction opportunities and their relationships with farmers. A digital survey was developed and sent out to Irish farm animal veterinarians. This paper presents the results of a cross-sectional study of Irish farm animal veterinarians’ attitudes towards antimicrobial stewardship, their prescribing behaviours, antibiotic reduction opportunities and their attitudes for the future of antibiotic use. The veterinarian-farmer relationship is examined and potential interventions to reduce antibiotic use on farms are identified.In total, 114 complete questionnaires were received, representing approximately 11 per cent of all farm animal veterinarians in Ireland. Respondents were aware of the problem of antibiotic resistance and recognise their role in the fight against it. They realise what actions they must take to reduce antibiotic use and identify barriers that prevent their farmer clients from implementing their advice. Many of them say that they can reduce antibiotic use on farms in the future, but some remain doubtful. There was no statistical difference between veterinarians that had less experience working than those that had more experience in their attitudes towards future reduction in antibiotic use.Most of the respondents seek to use antibiotics as judiciously as they can. The majority agree that antibiotic overuse is the main contributor to antibiotic resistance. Possible solutions to reduce antibiotic use include the development of antibiotic treatment guidelines, assigning one unique practice to each farm and compulsory CPD  courses.The online version contains supplementary material available at 10.1186/s13620-023-00253-w. Antibiotic resistance is considered as one of the biggest threats to human and animal health by the World Health Organisation . The WHOIn Ireland, antibiotics are classified as ‘Prescription Only Medicines’ by the Health Products Regulatory Authority . This meThe WHO recognises the surveillance of antibiotic use as essential in order to objectively measure any effect of any preventive action taken against antibiotic use and antibiotic resistance.Implementation of the new EU Veterinary Regulations 2019/6  on veterCurrently, there is little qualitative research available on the opinions of Irish veterinarians regarding antibiotic use, or of determinants that influence their prescribing behaviour and ways to promote prudent antibiotic use. Therefore, this study aimed to clarify the opinions of farm animal veterinarians in Ireland regarding antibiotic use, their prescribing behaviour with respect to antibiotics, the factors that influence prescribing, and on their attitudes to the future use of antibiotics. As part of the study, the veterinarian-farmer relationship will be investigated, including issues surrounding uptake of veterinary advice.The questionnaire was developed by the author after consulting an English translation of a previous questionnaire designed by Speksnijder and co-authors . This quSimilar to the Dutch questionnaire, the questionnaire was organised in sections that aimed to examine the following research objectives:Background of the study’s participantsParticipant opinions on antibiotic useExamining the farmer-veterinarian relationshipAttitudes for the future of veterinary antibiotic useSolutionsIn total, there were 49 questions, including 48 closed-ended questions and one open-ended question. The closed-ended questions were all multiple-choice questions with defined responses. Many were 5- scale Likert items, which presents respondents with an itemised scale from which to choose .With these questions, respondents were asked to indicate their degree of agreement to a stimulus object statement by selecting one of five descriptive categories . Other questions were a variation of Likert items with respondents asked to rank a given statement from “very important” to “not at all important”. There were also some ranking questions (rank in order of importance), to assess attitudes, knowledge and self-reported behaviour regarding antibiotic use and stewardship in food-producing animals. As part of the questionnaire, respondents were asked to estimate the amount of time they spent  with each of seven identified animal species/sectors: poultry, pigs, cattle for eventual slaughter , veal calves, sheep and goats, horses, and pets. The open-ended question enquired about the candidate’s number of years spent in practice.Following development, the questionnaire was piloted with 10 practicing farm animal veterinarians known to the author to ensure its ease of use and understanding. It took an average of 25 minutes to complete. Following feedback, it was adapted and sent out via weblink using SurveyMonkey®, an online survey platform.A copy of the questionnaire was sent to the researcher’s university for ethical approval, which was received, before it was distributed. The questionnaire is available in Annex http://www.veterinaryireland.ie) estimates there to be about 1,000 vets in Ireland that treat food-producing animals [The reference population included all farm animal veterinarians practicing in Ireland. Veterinary Ireland , many of whom work in farm animal practice [A non-probability, ‘snowball’ sampling method was used to enrol participants. A weblink (with an explanatory message) was sent directly to farm animal veterinarians known to the author with a request that the link be circulated more widely. It was also posted in the February and March 2022 editions of the practice .Survey participation was voluntary. After clicking the weblink, participants were firstly directed to a declaration of anonymity signed by the researcher before commencing the survey. All answers were anonymous, no personal data was collected other than the number of years spent in practice and university of study. The researcher’s contact details were posted at the beginning of the survey, to assist with any queries. Participants were informed of the objective of the survey mentioned above.Data were collected and managed in SurveyMonkey® and transferred to Microsoft Excel and Jamovi version 2.2.5) for analysis. Most data analyses were descriptive, to calculate means, counts and percentages. SurveyMonkey® was used to create stacked bar charts and pie charts of responses to the Likert item questions via its facility to export data to Microsoft Excel. Chi squared analyses were conducted to compare years of experience as a practice veterinarian . This variable was chosen as it marks a turn in global focus by the World Health Organisation and other governmental agencies to tackle antibiotic resistance. In 2015 the WHO described the emerging problem of antibiotic resistance as a global threat that required the “utmost urgency” [.2.5 for In total, 114 complete questionnaires were received, representing approximately 11 per cent of all farm animal veterinarians in Ireland. The average number of years of professional experience (in practice) of respondents was 9.7 years  had no more than seven years of practice experience), and 71.9 % graduated from the University College Dublin; 13.2 % from Budapest; 4.4 % from a UK university; 3.5 % from Warsaw and 7 % from elsewhere. 28.9 % described themselves as practice owners; 63.2 % as employees and 7.9 % as “other”.Table The responses of participants to statements relating to antibiotic use is presented in Table Cumulatively, 86.9% of respondents agreed that it is their goal to reduce antibiotic use on farms as much as possible.The familiarity of and usage by study participants with bacterial culture and antibiotic sensitivity testing (AST) is presented in Table p= 0.048) between years of experience and a respondent agreeing or not that their decisions around antibiotic prescription were influenced by farmers’ explicit demands. That is, more experienced veterinarians were less likely to be influenced by their clients’ demands, and less experienced veterinarians may prioritise client satisfaction over antibiotic stewardship in their prescribing habits.There was a statistically significant association  and 45 (39.5%) respondents suggesting that a 10-25% or 25-50% reduction, respectively, was considered possible in the next five years. The median value of respondents saw a 25% reduction in antibiotic use in cattle over the next five years. The species of pigs and poultry saw a lower reduction in antibiotic use predicted by respondents.Participants were asked their view of the statement that ‘general antibiotic use on farms in the near future is unlikely’. Among the 114 respondents, 28 strongly agreed or agreed with this statement, 15 neither agreed nor disagreed and 71 disagreed or strongly disagreed. In other words, 62.3% of respondents agreed that a reduction in on-farm antibiotic use is possible in the near future.Table Cumulatively, 73.7 % of respondents were in favour of compulsory CPD on antibiotic use for veterinarians.Respondents were also asked to rank various actions in order of importance to their contribution to reduce antibiotic use. The mode value in the list was ‘an education programme for farmers on correct antibiotic use and the need to protect them’. Fifty out of one-hundred and fourteen respondents listed this option as their number one in importance. The second highest rated action was ‘benchmarking of antibiotic use (tracking of vets and farmers) including sanctioning of high users’ and thirdly, ‘improving biosecurity on farms.’ These findings suggest a strong desire amongst Irish farm animal veterinarians for farmer education on correct antibiotic usage in order to reduce antibiotic use.This study offers insights in different attitudes of farm animal veterinarians in Ireland towards antibiotic use and antibiotic resistance in farm animals, and their interactions with farmers. Most of the respondents acknowledge their role in antibiotic stewardship and aim to administer them judiciously, though some respondents feel pressure to not refuse their farmer clients’ demands for antibiotics. This previous questionnaire found that most respondents were more likely to prescribe antimicrobials if the farmer wanted them and the majority of veterinarians thought that the farmer expected them. In this study, this was more common among the less experienced veterinarians. Many respondents are willing to apply antibiotics preventatively if they thought they could prevent disease, which is contrary to current EU regulations , 9. FarmMost respondents in this survey agreed that they would not hesitate to apply antibiotics prophylactically. This is at odds with the new EU regulation which prohibits the prophylactic use of antibiotics except in well-defined cases where each of the following three criteria are met: treatment is limited to an individual , the risk of infection is very high, and the consequences are likely to be severe . PrescriAntibiotic culture and susceptibility testing (AST) allows for a precise diagnosis of a causative bacteria and therefore, selection of the most appropriate antibiotic following this diagnosis. A 2013 study on AST frequency found that 37.8 % of EU veterinary practitioners  used AST before starting any antibiotic therapy, 9.8 % of them never requested it and 44.3 % used it on a seldom basis when prompted by a poor initial response to treatment , 17. TabTreatment guidelines may be an area for development given the responses from many respondents in this survey. Currently the RUMA (Responsible Use of Medicines in Agriculture Alliance) guidelines illustrate easy-to-read guiding principles for each animal sector that can be used by farmers and veterinarians . The BriAnimal Health Ireland (AHI) has developed specific (non-mandatory) guidelines for the treatment of mastitis as part of their Cell Check programme, both to assist with mastitis control and reduce the use of intramammary antibiotics . This wiThe Netherlands has had successful experience with the development and use of antibiotic formularies and, since 2013, the introduction of specific clinical guidelines (as described in ). These Many of the respondents found it difficult to be regarded as the primary advisor to their farmer clients given all the other advisors available. Respondents stated that they often encountered scenarios where disease could have been prevented if their advice had been followed. They agreed that farmers regularly apply antibiotics incorrectly. As Table Martin and co-authors  reflect With the introduction of the new EU veterinary regulations, benchmarking of individual veterinarians’ use or prescription of antibiotics as well as individual farmers’ use of antibiotics will now be possible. This has been a key factor in other EU member states, allowing for the identification of farms where use is particularly high, to guide further investigation and assistance, and sanctioning if necessary. For example. Jensen and co-authors demonstrated a causal association between a 25% decline in antibiotic use in the Danish pig population from 2009-2011 following the introduction of their ‘Yellow Card’ scheme that benchmarked high antibiotic use pig farms. This scheme contributed substantially to a reversal in the observed trend of increasing antibiotic use during 2002-2009 . BenchmaAny behaviour change must first start with acceptance of personal responsibility, so acknowledgement of the responsibility by the respondents in this survey in the fight against antibiotic resistance is very positive. Cumulatively, 86.8 % of survey respondents agree that their goal is to reduce antibiotic use on farms as much as possible and therefore recognise their role in antibiotic stewardship.The intensive sectors of pigs and poultry have been the focus of national attention in the past few years , 30, andPublic opinion may suggest that the more experienced or older generation veterinarians may be more likely to use more antibiotics and not see a change in antibiotic use possible. However, the results from this survey show no statistically significant difference between those veterinarians with less than or equal to seven years of experience and those that have more than seven years of experience.Opinions were taken on an approach to prescribing that has been adopted in the Netherlands, namely the assigning of a single prescribing practice to each farm . Under tThe new EU regulation allows veterinary antibiotic prescriptions to only last for five days  which wiBased on the results of this survey, this will be very beneficial as the veterinarians in this study have identified farmers’ misuse of antibiotics as one of the key factors in reducing the veterinary effect on antibiotic resistance.The response rate of 114 Irish farm animal veterinarians working with food-producing animals out of an estimated 1,000 strong workforce represents circa 11% of the Irish farm animal veterinarians’ population. As Table Among participants, the average amount of years spent in practice was 9.8 years. Given that most veterinarians qualify at twenty-four years of age, this is in line with a survey conducted by DAFM in 2020, which found more veterinary practitioners in large and mixed practices in the 30-39 age bracket (190 out of 674 interviewed) than in any other age bracket .By basing the bulk of the questions in this survey on previous research , resultsWith respect to the survey strategy that was utilised in this study, anonymity was seen as important, as a means to encourage participants to answer honestly. Candidates could not complete this survey without answering all the questions, thereby minimising concerns relating to missing data. A drawback of using the survey tool is the possibility of differing interpretations to the questions asked, particularly given that the questions in this survey are translated from the Dutch version . PilotinThe survey was designed in January 2022 and distributed in February and March 2022. This was around the same time that the new veterinary regulations , 7 were In conclusion, most of the Irish veterinarians in farm animal practice who participated in this study seek to use antibiotics as judiciously as they can, but there are some barriers to prudent prescribing. The development of antibiotic treatment guidelines, assigning one unique practice to each farm, and compulsory CPD courses were viewed by most respondents in this survey as possible solutions. Assuming these results reflect the views of most farm animal veterinarians in Ireland, these areas should be the focus for antibiotic resistance focus groups and development planning in the future. By working in accordance with the new veterinary medicine regulations that incorporate data recording on antibiotic use and collaborative educational schemes on antibiotic safeguarding, Irish veterinarians and farmers can help reduce antibiotic use on farm and subsequently, help combat antibiotic resistance.Additional file 1.


The increasing pressure of traffic congestion on socio-economic development has made the construction of cross-water transportation ever more crucial. The immersed tunnel method is among the most extensively employed. However, a critical challenge of the immersed tunnel technique is to ensure the compactness and stability of concrete during the casting process. Conventional laboratory methods face challenges in achieving large-volume concrete casting, resulting in the notable waste of human and material resources. Hence, this study employs a simulation approach to investigate the casting parameters and the fresh properties of concrete, exploring their impacts on concrete stability and compactness. The results indicate that when the surface tension of concrete exceeds 0.03 N/m, and the yield stress and plastic viscosity are 50 Pa and 50 Pa·s, respectively, the concrete exhibits excellent casting compactness. A design incorporating three large and six small outlets, paired with a casting speed of 3 cm/s, achieves superior compactness. Additionally, when the yield stress of concrete exceeds 3 Pa, there is no segregation of aggregates. In cases where segregation occurs, the thixotropic property of the cement paste contributes to a significant reduction in the velocity of aggregate segregation. With the rapid development of the socio-economy, there is an increasing demand for navigation both on and under water. The traditional method is to build bridges to facilitate the flow of people and goods, which is only suitable for low-demand waterways . In addiUnderwater tunnels have become a preferred choice for crossing rivers and seas due to their all-weather capabilities, large capacity, convenience, and low impact on shipping and the environment, among other navigation options ,4. CommoIn 1910, the Central Railway Tunnel in the Detroit River in the United States was the first steel shell immersed tube tunnel prepared using the immersed tube method . Over thStarting in the 1960s, Japan introduced a steel–concrete–steel composite structure . MoreoveDrawing from Japan’s technology, China, in similar circumstances, constructed the Hong Kong–Zhuhai–Macau Bridge Undersea Tunnel and the Shenzhen–Zhongshan Undersea Tunnel ,12. The The successful application of these steel shell-immersed tube tunnels is closely related to the development of self-compacting concrete (SCC) ,14. OrdiMany researchers have launched a series of experimental studies on the flowability of SCC and the casting process of steel shell-immersed tube tunnels. For example, Wang  studied With the popularization of theoretical models of concrete and computational fluid dynamics (CFD) analysis, numerical simulations of concrete flow have become more mature. Currently, numerical simulation methods for the simulation of concrete flow mainly include Fluent, STAR-CCM+, CATIA, and so on. Based on this, Thrane  used FidTherefore, this paper uses COMSOL finite element software (version 6.1), with secondary development, to study the influence of material properties and casting parameters on casting compactness within SCC mixtures and between steel plates and SCC, as well as the aggregate segregation of SCC. The parameters involved in this paper are the yield stress, plastic viscosity, surface tension of SCC, casting speed, number, and position of air outlets, etc.Since E.C. Bingham and others first proposed the Bingham fluid, it has been applied to materials such as porcelain clay and diatomaceous earth, characterizing the material properties through the definition of yield stress and plastic viscosity. Subsequent research by Tattersall and Banfill ,25 foundm is set to 100. However, according to the rheological curve of the Bingham model, as the strain rate astasiou  proposedby Jeong  and otheThe casting mold is shown in −2, which had good convergence. The “Two-phase flow-Laminar” model was employed to treat the fresh mixed SCC as a homogeneous Bingham fluid, examining the effects of the number of air outlets, concrete surface tension, rheological properties, and casting speed on casting compactness. In this model, the phase field method is used to capture the air–water interface when solving the Navier–Stokes equations. In addition, the interface position is tracked by the phase field variable equation and the mixing energy density equation . The mod3. A gravel size of 20 mm was chosen, with a density of 2800 kg/m3. The water-to-cement ratio of cement paste was set to 0.35. The contact angle between the concrete and the steel plate was set to 45°.The density of the concrete was set to 2400 kg/mThe yield stress and plastic viscosity of SCC were set to be 50 Pa and 50 Pa·s as a reference, according to Wallevik’s study . WalleviAdditionally, aggregate movement in concrete affects the performance of concrete, as well as its construction stability and safety. In recent years, in the numerical simulation studies of liquid–solid two-phase flow, the Euler–Euler method and the Euler–Lagrange method are commonly used . Among tt is the time, The Euler–Lagrange method treats the fluid phase as a continuous phase and the particle phase as a discrete system, which allows the trajectories of all the particle phases to be tracked. On the one hand, the Eulerian method is used to deal with the motion of the fluid phase by borrowing the form of the single-phase flow equations to calculate the equations of control of the motion of the fluid, and using the Navier–Stokes equations of the coupled liquid-solid two-phase system to describe the laws of motion of the fluid phase . On the T, m and α are thixotropic parameters.As long as steady-state flow is reached, the behavior of fresh concrete can be described using a yield stress model such as the Bingham or Hershel Bulkley models. However, in the case of cementitious materials, things are not so simple as the hydration process starts as soon as cement and water are mixed together. The apparent viscosity of the material is permanently evolving, as described by Otsubo et al. . This phd/h, where d is the distance between outlet and mold boundary, and h is the distance between the inlet and mold boundary) exceeded 0.2, a noticeable debonding zone appeared in the upper-left corner of the mold, and the closer the outlet was to the casting inlet, the larger the debonding zone. In this study, a small-scale mold was first used to examine the general impact of the number and layout of outlets on casting compactness. The effect of one outlet on casting compactness was first studied, as shown in d/h exceeded 0.4, a noticeable debonding area appeared between the two outlets, and the debonding area increased as d increased. Consequently, three outlets were used, as shown in Based on this, an additional outlet was introduced to study casting compactness, as shown in Next, using the three outlets as an example, the influence of casting speed on casting compactness is studied, as illustrated in SCC can be considered as a Bingham fluid with yield stress and plastic viscosity ranging from 25 Pa, 25 Pa·s to 100 Pa, 100 Pa·s, respectively ,36,37. TMoreover, the effect of plastic viscosity on casting compactness was investigated, as shown in The air content of SCC under different surface tensions was investigated, and four different surface tensions of 0.0001 N/m (which is an extreme case), 0.02 N/m, 0.03 N/m, and 0.063 N/m were simulated; the results are shown in When the surface tension was further increased to 0.03 N/m and 0.063 N/m, as shown in The difference between the full-scale mold and the small-scale mold was further investigated based on the small-scale mold. Since the full-scale mold is large and requires a lot of computational resources, we first chose the full-size with a high casting speed (20 cm/s), as shown in The effect of the number of outlets and their layout on the casting compactness was explored, as shown in Moreover, it is obvious that there is a difference between the results of the simplified full-scale mold and those of the small-scale mold, as shown in Moreover, the discussion on the effect of the casting rate on content was further analyzed. Two different velocities were chosen, 3 cm/s and 0.75 cm/s, as shown in d is the size of the particle (d = 2 cm in this work),and g is the gravitational acceleration (g = 9.8).According to N. Roussel’s  study onThe expected value of Therefore, the yield stresses of 2 Pa and 4 Pa are selected to study the segregation performance of aggregates. It can be found that the aggregates do not have any segregation and are stably suspended in the cement paste when the yield stress of the cement paste is 4 Pa, as shown in The thixotropic and Bingham models were used simultaneously to describe the effect of changes in cement paste viscosity on aggregate segregation. The simulation results are shown in In addition, it can be seen from In this paper, a casting mold was constructed using COMSOL finite element simulation for small-scale as well as full-scale casting. The effects of the number and layout of the outlets and the speed of casting, as well as the surface tension, yield stress, and the plastic viscosity of the concrete, on the casting compactness were investigated. The effects of the yield stress and plastic viscosity of concrete on aggregate segregation were also investigated.In the small-scale mold, the final debonding area decreased significantly as the number of air outlets increased. When the number of outlets was one or two, there was eventually an obvious debonding area, and when the number of outlets was three, no debonding area existed no matter how the outlets are arranged. Taking the three-outlets mold as an example, with the increase in the casting speed, the debonding area increased significantly. When the casting speed was less than 10 mm/s, there was no debonding area, mainly because a slower speed allowed the SCC to have enough time to flow uniformly. The influence of the number and layout of air outlets on the casting compactness in the full-scale mold was different from that in the small-scale mold. As the number of air outlets increased, the final debonding area decreased. However, in the full-scale mold, no matter if the number of outlets changed from one to three, there was still a debonding area in the final mold. This was mainly because in the full-scale mold, although it had the same layout of outlets as in the small-scale mold, the distance between every two outlets was still very large, so it was difficult to use the results of the small-scale mold as a guideline for the full-scale mold. Then, the effect of casting speed was studied, and it was found that reducing the speed still could not reduce the debonding area. On this basis, six small outlets were added around the large outlets, and this layout successfully eliminated the debonding area. Thus, in the small-scale mold, one can construct three air outlets and guarantee a low casting speed (less than 10 mm/s). However, in a full-scale mold, one may consider adding small outlets on the basis of three large outlets to increase the airflow . The surface tension of the concrete affects the air content of the concrete. When the surface tension was too low (less than 0.02 N/m), the SCC easily involved a large amount of air, so the final air content was higher. When the surface tension was too high, less air was entrained, but the air bubbles were difficult to burst and remained in the concrete. When the surface tension was more than 0.03 N/m, it could reduce the strength and stability of the bubble film, accelerate the exclusion of the liquid around the bubble, and make the liquid film thinner and rupture, thus eliminating the bubbles and decreasing the air content of the SCC. The yield stress and plastic viscosity of concrete will also affect the compactness of casting. When the yield stress and plastic viscosity were too low (25 Pa and 25 Pa·s), the SCC was too thin and could easily involve a large amount of air, resulting in a high air content. When the yield stress and plastic viscosity were too high (100 Pa and 100 Pa·s), the SCC was too viscous and it was difficult to flow uniformly on the surface, so the debonding area would eventually form. Only when the yield stress and plastic viscosity were moderate (50 Pa and 50 Pa·s) did the SCC flow easily on the surface and not trap large amounts of air.From the above analysis of the debonding area, it can be seen that this debonding phenomenon was mainly due to the insufficient number of outlets or excessive material viscosity and yield stress, resulting in air not being removed from the mold in a timely manner, so that aggregation occurred at the top, which led to the formation of a debonding phenomenon.Finally, the relationship between the aggregate segregation properties and the rheological properties of the interstitial cement paste was studied. Taking the largest aggregate particle size of 2 cm as an example, it was found that when the yield stress of the cement was higher than 3 Pa, the aggregate could be stable in the cement paste, and when the yield stress was lower than 3 Pa, the aggregate would segregate. When segregation occurred, as the yield stress of the paste kept increasing due to its thixotropic feature, the velocity of aggregate segregation was greatly reduced compared to the case where there was no thixotropic feature. Thus, it makes sense to use the thixotropic model to consider the segregation properties of aggregates in cement.In the real world, the design of different concrete mixing proportions is inevitable in engineering, and they will affect the important rheological parameters in this paper, including yield stress and plastic viscosity. Concrete with too high a flowability (yield stress and plastic viscosity less than 50 Pa and 50 Pa·s) will not debond from the mold, but too low a yield stress will lead to segregation of the aggregates and is not suitable for practical engineering. Concrete with too low a flowability (yield stress and plastic viscosity great than 50 Pa and 50 Pa·s) will not easily remove air from the mold, resulting in debonding of the concrete from the mold, which is also unsuitable for practical engineering. However, concrete with a moderate flowability (yield stress and plastic viscosity are 50 Pa and 50 Pa·s) can keep the aggregates from segregating, and at the same time, the concrete will not debond from the mold. Therefore, a yield stress and plastic viscosity of 50 Pa and 50 Pa·s is an excellent choice for practical engineering.In addition, considering the problems of bonding between fresh concrete and a steel shell, and the shrinkage of hardened concrete, some surfactants with a shrinkage-reduction function are usually added, which can reduce the surface tension of concrete significantly (as low as 0.03–0.063 N/m). According to the study of surface tension in this paper see , a propeHowever, this paper mainly considered the early rheological properties of concrete and its debonding from the steel shell. In future work, it is necessary to further consider the debonding of hardened concrete from the steel shell due to shrinkage or cracking. In addition, whether switching to a different casting mold, such as wood or plastic, will produce different results from steel shell casting under the same casting parameters needs further verification and simulation.In this paper, a steel shell mold for the concrete casting of immersed tube tunnels was constructed using COMSOL finite element software (version 6.1). The influence of the number and layout of outlets and the speed of casting, as well as the surface tension, yield stress, and the plastic viscosity of SCC on the casting compactness and air content are investigated. In addition, the effects of the yield stress and plastic viscosity of the cement paste on aggregate segregation were also discussed. The main conclusions are as follows.When the surface tension of SCC is greater than 0.03 N/m, there is excellent casting compactness. Furthermore, the addition of an appropriate amount of surfactant to SCC can help to reduce the air content of SCC, which can further improve the casting compactness. Moreover, when the yield stress and plastic viscosity are 50 Pa and 50 Pa·s, respectively, the SCC exhibits great casting compactness. Additionally, the layout of the outlets has different effects on casting compactness in the full-scale and small-scale molds. In small-scale mold, the compactness of casting is decent when the number of outlets is three and the casting speed is lower than 10 mm/s. However, it is necessary to incorporate three large and six small outlets paired with a casting speed of 3 cm/s in the full-scale mold for superior compactness. In addition, when the yield stress of cement paste exceeds 3 Pa, there is no segregation of aggregates. In the case of aggregate separation, the rate of aggregate segregation decreases as the viscosity of the cement paste increases. On this basis, when the thixotropic properties of the cement paste are taken into account, it is found that the rate of aggregate segregation decreases significantly.In future work, further aspects of the geometry of casting molds will be investigated. In addition, we need to check the morphology of the aggregate and the particle size distribution on the casting compactness between SCC and the mold.


Autonomous healing is a very promising technique in self-healing concrete systems. For capsules to achieve their anticipated performance, they should be able to survive the harsh mixing conditions of concrete, yet rupture upon concrete cracking. At present, there are no standard test methods, either experimental or analytical, for determining the capsule survival rate during concrete mixing. This study investigates the correlation between the capsules’ shell properties, concrete rheological properties, the capsules’ external forces, and capsule survival rate during concrete mixing. Finite element and statistical modeling techniques were employed to evaluate the capsule performance and predict the survival rate of capsules during concrete mixing, with 68% confidence. The results revealed that the capsules’ survivability during concrete mixing is highly influenced by the capsule’s radius-to-thickness ratio, the rheological properties of the fresh concrete, the average-paste-thickness (APT) of the concrete mix, the aggregate content and angularity, and the speed of the mixer. In brief, capsules with a radius-to-thickness ratio between 30 and 45 are likely to survive concrete mixing and yet still rupture upon concrete cracking. Encapsulation, which is employed to protect the healing agent during the mixing and casting of fresh concrete and to release the agent upon the cracking of hardened concrete ,2, is a The survivability of capsules during concrete mixing is pivotal to the effectiveness of self-healing concrete systems. As the vessel for the healing agents, if the capsules were ruptured during mixing, then their presence in the self-healing cementitious matrix becomes detrimental to the mechanical properties of the concrete matrix. Among several encapsulation materials investigated in the literature for their suitability in self-healing concrete applications, glass and ceramics have shown limited ability to survive mixing conditions, both requiring protective techniques to enhance their ductility ,48,50,51The review of the literature revealed two testing methodologies that have been adopted to investigate the survivability of self-healing capsules: (1) chemical stability ,52,53,54The chemical stability test, which consists of immersing the capsules in a high pH solution, mimicking concrete pore solution, followed by a mechanical test, aims to ensure that the capsules’ mechanical properties are not altered by the concrete pore solution. The tensile strength of PLA, PS, and P(MMA-n-BMA) tubes was tested before and after immersing them in cement slurry with a pH of 12.5 to 13 for 7 to 14 days. The results revealed that only the P(MMA/n-BMA) tubes’ strength was lower . Other rTesting the mechanical stability during mixing was reported for large-size capsules, with a visual count employed to determine the number of intact capsules. The developed tests consist of mixing the fresh concrete, then sieving it under running water to capture the surviving capsules. Hu et al.  mixed 10Standardized tests to evaluate the survivability of capsules during concrete mixing are needed.Test results show that capsules have the required chemical resistance to survive in a high alkaline concrete pore solution.Capsule survival rate, according to chemical and/or mechanical tests, is deduced from visual inspection of a few capsules and assuming that the sample is representative of the whole sample. The statistical properties of the sample must be established before accepting such an approach.The type of mixer, speed of mixing, mixing time, and mixing technique varied between different studies, which makes it difficult to compare the results, even for the capsules made with the same materials.Concrete rheological properties affect the capsule survivability rate.Capsules in mortar have a higher survivability than those added to concrete.Capsules with a smaller diameter and thicker walls have a higher survival rate.From the previous studies, the following observations can be made:Finite element and statistical modeling techniques were employed for determining the survivability of polymeric capsules in a concrete mixer. Experiments carried out by the authors and data reported in the literature were used to quantify the rheological properties of fresh concrete and the mechanical and geometrical properties of polymeric capsules, respectively. It was postulated that the rheological properties of concrete and the rotational speed of the mixer affect the shearing stress and normal stress exerted on the capsules during mixing, respectively. Standard deviation was the measurement used to account for the variability in the capsules’ geometrical and mechanical properties. The interactions between the input variables and the capsule survival rate were predicted with 68% confidence. Details of the material properties, model development, and design of the experiments are provided next.3, and 1.58%, respectively. The fineness modulus, specific gravity, bulk density, and absorption of fine aggregate are 2.88, 2.71, 1746 kg/m3, and 1.28%, respectively. The bulk density, specific gravity, and absorption of coarse and fine aggregates were determined in accordance with ASTM C127-15 [Two self-consolidating concrete (SCC) mixes, designed to have a minimum slump flow of 600 mm, were used in this study. A ring-pan mixer , and vis C127-15  and ASTM C127-15 , respect C127-15  and CSA  C127-15 , respect C127-15 , along w C127-15 ,69,70, wFor the capsule, two values for the diameter and thickness were considered, along with a single value for the rupture strength and fracture energy, as given in The model consists of a single capsule located at the bottom and outer edge of the concrete mixer. The free-body diagram of the capsule in a rotating concrete mixer is shown in ρ is the density of the fresh concrete (kg/m3), 2). The thickness of the concrete layer is deduced from the size of the mixer and its maximum concrete yield.The weight (md is the diameter of the mixer (m), and 3 of concrete, 2.425 m, and 26 rpm, respectively.The centrifugal force  model was developed for this analysis using the commercial finite element program ABAQUS . The FE The cohesive interface surface model, developed by ABAQUS , was empThe numerical experiments were designed to determine the interactions between the input parameters and the output, specifically, the survival of the capsules. Two diameters and two thicknesses of the capsule were included. The mean plus and minus one standard deviation were analyzed for the capsule geometry and the capsule rupture strength. Moreover, two loadings were considered to account for the interactions between the capsules and the concrete paste, and the capsules and the aggregates. The analyses executed are summarized in rs = 30.0 ± 2.5 MPa, and the elongation limit of the urea-formaldehyde shell is 0.75 ± 0.08% [The results revealed two potential failure modes for the capsule, as shown in  ± 0.08% .The FE analyses, which yielded the shell state of the stress and strain, as well the survivability of the capsule, when subjected to squeezing and stretching by concrete paste and pinching by aggregates, are summarized in f), are presented in f was determined on the assumption that 90% of the capsules are surrounded by concrete paste and 10% by aggregates. From the results of f, with the assumption that 100% of the capsules are surrounded by concrete paste and 0% by aggregates, the results become 0.0%, 1.3%, 2.6%, and 1.9%, respectively. These results reveal that (1) the rheological properties of the concrete mix affect the survivability of small size capsules and that the effect decreases with an increase in capsule diameter; (2) the survivability of the capsule decreases as the capsule size increases, regardless of the rheological properties of the concrete; (3) the interaction of aggregates with the capsules significantly affects the survivability of the capsules; and (4) on average, 90% of the capsules are expected to survive the mixing of concrete, given a material rupture strength of 30 ± 2.5 MPa and elongation limit of 0.75 ± 0.08%.Assuming the results follow a normal distribution, the probability of capsule failure based on a 68% confidence level was analyzed using the finite element results and the corresponding material properties. The three failure modes were analyzed separately, and the results, in the form of probability of failure (PThe FE results are found to agree with Souza and Al-Tabbaa experimental data . Their SResearch studies on the survivability of self-healing capsules during concrete mixing are found to be lacking despite its significance to the performance of self-healing concrete system.The capsules’ radius-to-thickness ratio highly influences the survivability of the capsules during concrete mixing.The rheological properties of fresh concrete affect the survivability of small-sized capsules, and that effect decreases with an increase in capsule diameter.The interaction between the aggregates and the capsules adversely affects the survivability of the capsules.In capsules whose radius-to-thickness ratio is greater than 45, the probability of failure increases from 0 to 10%.The combined effect of the concrete’s rheological properties and capsules’ geometry on the capsules’ probability of failure increased from 10% to 26% for mix #2 when the capsules’ radius-to-thickness ratio was between 60 and 80, and from 10% to 13% for both mixes when the capsules’ radius-to-thickness ratio was between 80 and 90.The survivability of the capsule decreases to 90% when the capsules’ radius-to-thickness ratio is greater than 90, regardless of the concrete rheological properties.This paper presents a finite element model for studying the survivability of capsules during concrete mixing. The model considers all possible interactions between the capsules and the surroundings, as well as accounts for the geometry of the capsules and the rheological properties of the concrete. The probabilities of capsule failure were determined using statistical models and assuming a normal distribution. Accordingly, the following conclusions are drawn:The recommendations are to design self-healing concrete system with a capsule radius-to-thickness ratio between 30 to 45 to survive concrete mixing and yet still rupture upon the cracking of hardened concrete, and that a standard test should be developed to account for the capsule geometry and material properties; the concrete rheological properties; the concrete mix design, specifically the APT, the aggregate content, and the angularity; and the speed of the mixer. Lastly, the findings, conclusions, and recommendations are specific to the variables investigated in this study.