To develop and validate a sensitive and rapid ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the determination of enasidenib in rat plasma and to investigate the effect of Xiao-ai-ping injection (XAPI) on the pharmacokinetics of enasidenib in rats.  The rat plasma was precipitated with acetonitrile, enasidenib and internal standard (IS) were separated on an Acquity UPLC BEH C18 column, and acetonitrile and 0.1% formic acid were used as the mobile phase in gradient mode. Enasidenib and IS were monitored and detected by multiple reaction monitoring (MRM) using tandem mass spectrometry in positive ion mode. 12 Sprague-Dawley (SD) rats were randomly divided into control group (group A) and experimental group (group B), 6 rats in each group. Group B was intramuscularly injected with XAPI (0.3 mL/kg) every morning, 7 days in a row. Group A was intramuscularly injected with normal saline, 7 days in a row. On the seventh day, enasidenib (10 mg/kg) was given to both groups 30 min after injection of normal saline (group A) or XAPI (group B), and the blood was collected at different time points such as 0.33, 0.67, 1, 1.5, 2, 3, 4, 6, 9, 12, 24, and 48 h. The concentration of enasidenib was detected by UPLC-MS/MS, and the main parameters of pharmacokinetic of enasidenib were calculated using the DAS 2.0 software. Cmax of enasidenib in the group A and the group B was (458.87 ± 136.02) ng/mL and (661.47 ± 107.32) ng/mL, t1/2 was (7.74 ± 0.91) h and (8.64 ± 0.42) h, AUCt)(0 −  was (4067.24 ± 1214.36) ng·h/mL and (5645.40 ± 1046.30) ng·h/mL, AUC(0 − ∞) was (4125.79 ± 1235.91) ng·h/mL and (5759.61 ± 1078.59) ng·h/mL, respectively. The Cmax of enasidenib in group B was 44.15% higher than that in group A, and the AUCt)(0 −  and AUC(0 − ∞) of enasidenib in group B were 38.80% and 39.60% higher than that in group A, respectively, and the t1/2 was prolonged from 7.74 h to 8.64 h.  Under the current experimental conditions, this UPLC method showed good linearity in the detection of enasidenib. Interday and intraday precision did not exceed 10%, the range of accuracy values were from -1.43% to 2.76%. The results of matrix effect, extraction recovery, and stability met the requirements of FDA approval guidelines of bioanalytical method validation. The  An UPLC-MS/MS method for the determination of enasidenib in rat plasma was established. XAPI can inhibit the metabolism of enasidenib and increase the concentration of enasidenib in rats. It is suggested that when XAPI was combined with enasidenib, the herb-drug interaction and adverse reactions should be paid attention to, and the dosage should be adjusted if necessary. Herb-drug interaction (HDIs) is a major health problem worldwide due to the potential risk of adverse reactions. The pharmacokinetic and pharmacodynamic changes resulting from this interaction may result in toxic or subtherapeutic outcomes associated with adverse clinical outcomes . A largeMarsdenia tenacissima, and the main components of XAPI contain phenolic acids and steroidal glycosides, among other compounds [+ T cells, thus, enhancing the antigrowth effect of cisplatin on Lewis lung carcinoma (LLC) xenogeneic mice, which provides new evidence for the clinical application of XAPI and cisplatin [Xiao-ai-ping injection (XAPI) is an injection extracted from Chinese herbal medicine ompounds , 4. In rompounds . XAPI caisplatin . XAPI coisplatin .Enasidenib Idhifa®,  is an orThere is also growing interest in the use of complementary and alternative medicine (CAM). 30% to 70% of patients with cancer have used CAM. In the daily management of cancer patients, herb-drug interactions (HDIs) should not be ignored by healthcare providers . By contIn recent years, the antitumor effect of XAPI has been further confirmed, and it has been widely used in the treatment of gastric cancer, lung cancer, esophageal cancer, and other malignant tumors. In the treatment of advanced gastric cancer, XAPI combined with chemotherapy is commonly used. Studies have shown that the extract of XAPI can interfere with the activities of CYP3A4 and CYP2D6 . So, it Therefore, according to the previous research on the methodology of detecting enasidenib by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) , in thisEnasidenib (purity above 98%) was purchased from the Beijing sunflower Technology Development Co., Ltd. Ivosidenib (purity over 98%) was purchased from sigma Aldrich (Shanghai) Trading Co., Ltd. HPLC grade formic acid was purchased from anaqua chemicals, Wilmington, USA. Acetonitrile and methanol of HPLC level were obtained from Merck Company . Purified water was produced by utilizing a Milli-Q academic reagent grade water purification system .XAPI  was purchased from Nanjing Shenghe Pharmaceutical Co., Ltd. .Accurately weigh enasidenib and ivosidenib in different volumetric flasks, dissolve them with methanol, and prepare enasidenib and ivosidenib stock solution with the concentration of 1.0 mg/ml, respectively. Then, the stock solution was diluted with methanol to obtain various working solutions for calibration curve and quality control (QC) of enasidenib. The final concentrations of the calibration curves of enasidenib were as follows: 1, 5, 10, 50, 100, 250, 500, and 1 000 ng/mL. As for QC samples, they were made in the same way at three concentration levels , and the concentrations of QC samples in plasma were 2.5, 250, and 750 ng/mL. The IS working solution (500 ng/mL) was also prepared by diluting the stock solution of ivosidenib with acetonitrile. All solutions were stored in a refrigerator at -20°C.μm), and the temperature was set at 45°C. The mobile phase consisted of 0.1% formic acid in acetonitrile (A) and 0.1% aqueous formic acid (B), and the scheme was implemented as follows: 0-1.4 min (30%⟶85% A) and 1.4-2.0 min (85%⟶30% B). The flow rate was set at 0.40 mL/min, and the total run time was 2.0 min.The chromatographic column was Acquity BEH C18 column  was used to realize the control and data acquisition of the instrument.Mass spectrometry was conducted on a XEVO TQ-S triple quadrupole mass spectrometer equipped with a positive ion electrospray ionization (ESI) interface. Multiple reaction monitoring (MRM) mode was used to measure enasidenib with transitions of μL rat plasma into 1.5 mL EP tube, add 10 μL of ivosidenib IS working solution (500 ng/mL), vortexed for 15 s, and add 200 μL of acetonitrile. After vortex mixing for 1.0 min, centrifugation was performed at 10000 rpm for 15 min. 2 μL of supernatant was taken and detected in UPLC-MS/MS system.Accurately suck 50 Validation is the basis of biological sample analysis. All the pharmacokinetic results depend on the analysis of biological samples. Only reliable methods can get reliable results. The established method should be verified through the study of accuracy, precision, specificity, sensitivity, recovery, stability, etc. According to technical guidelines for nonclinical pharmacokinetics of drugs of CFDA (China Food and Drug Administration) and the principles of Industry Bioanalytical Method Validation proposed by FDA, the method was validated , 18.The analytical method should be able to distinguish the target analyte from the endogenous components of the IS and matrix or other components in the sample. Blank plasma samples from six different rats were used to demonstrate selectivity, which is generally acceptable when the response of the interfering component is less than 20% of the response to the lower limit of quantitation (LLOQ) of the analyte.y) and theoretical concentration of enasidenib as abscissa (x), the standard curve was drawn with the least square method, and the weight factor was 1/x2. The LLOQ was regarded as the minimum value of the calibration curve when the value of S/N is more than 10, with accuracy  at ±20% and precision  below 20%.The response of the instrument to the analyte should be evaluated within the specified concentration range to obtain the standard curve. The final concentrations of the calibration curves of enasidenib were as follows: 1, 5, 10, 50, 100, 250, 500, and 1 000 ng/mL. Taking the peak area ratio of enasidenib to IS as ordinate . Eighteen repeated measurements, at three separate days, were used to calculate interday precision and accuracy at three QC concentrations . RSD% represents the precision while RE% expresses the accuracy.For matrix effect, the ratio of peak area in the presence of matrix (measured by adding enasidenib and IS after extraction from blank matrix) to corresponding peak area without matrix (pure solution of enasidenib and IS) should be calculated. The calculation of extraction recovery was analyzed through dividing each analyte response spiked to drug-free plasma prior to extraction by the concentration after extraction. The extraction recovery as well as the matrix effect was determined in six replicates at three QC concentrations .The stability of three QC concentrations  under four different conditions was studied. They were samples with three freeze-thaw cycles, samples at 4°C for 4 h in automatic sampler, samples at room temperature for 2 h, and samples stored at -20°C for 4 weeks. In this study, the stability of enasidenib in rat plasma was evaluated by analyzing five plasma samples with different concentrations.Twelve SD rats were provided by the Laboratory Animal Center of Henan University of Science and Technology, and the animal production license number was SCXK (Hubei) 2010-0007. All experimental animals were authorized by the Ethics Committee of Medical Department of Henan University of science and technology and used on the basis of experimental animals. The experiment was approved according to the Laboratory animals—guidelines for ethical review of welfare (GB/T 35892-2018). The animal feeding conditions were as follows, temperature of 16~28°C, relative humidity of 40% ~70%, and feeding twice a day. One day before the experiment, all rats stopped feeding and were free to drink water.Twelve SD rats were randomly divided into control group (group A) and experimental group (group B), 6 rats in each group. Group B was intramuscularly injected with XAPI (0.3 mL/kg) every morning, 7 days in a row. Group A was intramuscularly injected with normal saline, 7 days in a row. On the seventh day, enasidenib (10 mg/kg) was given to both groups 30 min after injection of normal saline (group A) or XAPI (group B), and the blood was collected from the tail vein of each rat and put into 1.5 mL heparinized tubes, and at different time points such as 0.33, 0.67, 1, 1.5, 2, 3, 4, 6, 9, 12, 24, and 48 h. The blood samples were collected into polyethylene tubes containing heparin; the plasma was taken and frozen at -20°C until analysis.The concentration of enasidenib in rat plasma of group A and group B was detected by the abovedeveloped UPLC-MS/MS method, according to the method of batch analysis. Blank rat plasma was used as the matrix to prepare the plasma standard curve and QC samples. Prepare the accompanying standard curve and measure the quality control sample to ensure the reliability of the biological sample analysis data.P values were calculated using the Independent sample t-test, and P < 0.05 was considered statistically significant.The DAS 2.0 software was used to calculate the main pharmacokinetic parameters of enasidenib with the noncompartmental analysis. The data were expressed as mean ± standard deviation (SD). The data were processed using SPSS 18.0 statistical software. Under the current experimental conditions, enasidenib and IS could be well separated. The representative chromatograms were shown in y = 1.5 × 10−3 x − 1.34 × 10−2 (R2 = 0.999 3). y represents the peak area ratio (enasidenib peak area/IS peak area), and x represents the plasma concentration of enasidenib. The LLOQ of enasidenib was the minimum concentration of the standard curve (1 ng/mL).In the range of 1–1 000 ng/mL of the plasma concentration of enasidenib, the typical regression equations of enasidenib were The results obtained for the intraday precision and interday precision of enasidenib were shown in The recovery and ME results were investigated and shown in All results for the stability samples test are summarized in Cmax of enasidenib in group B was 44.15% higher than that in group A, and the AUCt)(0 −  and AUC(0 − ∞) of enasidenib in group B were 38.80% and 39.60% higher than that in group A, respectively, and the t1/2 was prolonged from 7.74 h to 8.64 h. At the same time, CL was smaller and MRT was longer in group B than that in group A. The results showed that XAPI could slow down the metabolism of enasidenib and increase the plasma drug concentration of enasidenib in rats.The plasma concentration-time curve of enasidenib was shown in The UPLCMS/MS method for the determination of enasidenib in rat plasma using ivosidenib as the internal standard has high sensitivity, short analysis time, and simple sample operation. In order to obtain a shorter analysis time and more symmetrical peaks, we optimized the chromatographic conditions, including chromatographic column and mobile phase. The Acquity UPLC CSH C18 column, BEH C18 column, and HSS C18 column were evaluated. The results showed that enasidenib and IS had good separation on the UPLC BEH C18 column. We investigated the mobile phase ratio of acetonitrile, methanol, formic acid, and acetic acid under different conditions. The results showed that when acetonitrile and 0.1% formic acid were used as the mobile phase, the chromatographic peak was the best.Multiple reaction monitoring (MRM) was a commonly used analytical method for mass detection. It has the outstanding advantages of strong specificity, high sensitivity, high accuracy, good reproducibility, wide linear dynamic range, and high-throughput automation . At the The incidence of herb reactions affected by TCM preparations may be more frequent than expected clinically because patients are more likely to self-administer without informing their healthcare providers. Some interactions may have beneficial effects by improving drug efficacy or reducing potential side effects. However, more often than not, the combination of herbal products and traditional medicines may bring about potential side effects and outcome effects, which are always difficult to predict .Chinese medicine as an important means of cancer treatment in China has a history of many years. Traditional Chinese medicine (TCM) can inhibit the growth of tumor and prolong the survival rate of cancer patients . But herCmax of enasidenib in group B was 44.15% higher than that in group A, and the AUCt)(0 −  and AUC(0 − ∞) of enasidenib in group B were 38.80% and 39.60% higher than that in group A, respectively, and the t1/2 was prolonged from 7.74 h to 8.64 h. CL was smaller and MRT was longer in the experiment group than that in the control group. The results showed that XAPI could slow down the metabolism of enasidenib and increase the plasma concentration of enasidenib in rats. Therefore, when XAPI and enasidenib should be combined clinically, the dosage should be adjusted to ensure the efficacy to avoid adverse reactions.Enasidenib is a new and first-class oral small molecule inhibitor of IHD2. It is a noncytotoxic differentiation agent, which plays a role in inducing malignant cells to mature . EnasideA method for the determination of enasidenib in rat plasma was established. XAPI can inhibit the metabolism of enasidenib and increase the concentration of enasidenib in rats. It is suggested that when XAPI is combined with enasidenib, the herb-drug interaction and adverse reactions should be paid attention to, and the dosage should be adjusted if necessary.


To compare the proportion of therapy failure, recurrence and complications within 30 days after consultation between men diagnosed with lower urinary tract infection (UTI) treated with narrow-spectrum antibiotics (nitrofurantoin or pivmecillinam) and broad-spectrum antibiotics (fluoroquinolones or trimethoprim or trimethoprim/sulfamethoxazole).A retrospective cohort study based on data derived from electronic medical records between January 2012 and December 2015.Primary health care and hospital care in five different counties in Sweden.Patients: A total of 16,555 men aged between 18 and 79 years diagnosed with lower UTI.Treatment with narrow-spectrum antibiotics was compared with broad-spectrum antibiotics regarding therapy failure, recurrence and complications within 30 days.p < 0.001), but no such difference could be detected regarding complications.The median age of included men was 65 IQR (51–72) years. Narrow-spectrum antibiotics were prescribed in 8457 (40%) and broad-spectrum antibiotics in 12,667 (60%) cases, respectively. Therapy failure was registered in 192 (0.9%), recurrence in 1277 (6%) and complications in 121 (0.6%) cases. Therapy failure and recurrence were more common in patients treated with narrow-spectrum antibiotics and trimethoprim (Complications such as pyelonephritis and sepsis are uncommon in men diagnosed with lower urinary tract infection treated with antibiotics.There was no difference in incidence of complications among men diagnosed with lower urinary tract infection treated with narrow- or broad-spectrum antibiotics.In spite of higher incidence of therapy failure and recurrence, treatment with narrow-spectrum antibiotics seems to be an optimal choice regarding preventing complications when treating men diagnosed with lower UTI.There was no difference in incidence of complications within 30 days between men treated with narrow- or broad-spectrum antibiotics. Patients prescribed broad-spectrum antibiotics had lower odds of reconsultation because of therapy failure and recurrence. From current data, treatment with narrow-spectrum antibiotics seems to be an optimal choice regarding preventing complications when treating men with lower UTI. The incidence of urinary tract infection (UTI) in men varies with age and is uncommon (0.9 to 2.4 cases per 1000 men per year) in those younger than 55 years ,4. Thus,Escherichia coli (E. coli). During the past decades, the number of E.coli resistant to the former first-line antibiotics, fluoroquinolones, trimethoprim and trimethoprim/sulfamethoxazole (i.e. broad-spectrum antibiotics) have increased [The most common bacteria causing UTI in men is ncreased . This hancreased ,7. Fluorncreased . Guidelincreased . Accordincreased ,8.The new treatment recommendations for male UTI are based largely on studies conducted in women and children, and on clinical data that support treatment with pivmecillinam and nitrofurantoin for 5–7 days in women with lower UTI . The guiThe change in treatment recommendation has contributed to an alteration in treatment regime by prescribers. The sales of fluoroquinolones to men in 2017 decreased by 4.3% compared with 2016, while the sales of pivmecillinam and nitrofurantoin to men increased by 4.1% and 10.3%, respectively [Therefore, the aim of this study was to compare the proportion of therapy failure, recurrence and complications within 30 days after treatment for lower UTI between men treated with narrow-spectrum antibiotic and broad-spectrum antibiotics.This retrospective study was based on information derived from Swedish electronic medical records (EMR). The population was 883,449 men in 2012 with a 2.9 percent increase until 2015. We included men from 289 primary healthcare centres and 20 hospitals in five counties in southern and central Sweden. Data for all men aged 18–79 years diagnosed with lower UTI or complications pertaining to UTI in primary health care (PHC) and hospital care from January 2012 to December 2015 were identified through the EMR databases of Jönköping, Kalmar, Kronoberg, and Uppsala county. From Skåne county, data on lower UTI diagnoses in primary care and complications diagnosed in primary care and hospital care were collected from December 2012 to December 2015. However, it was not possible to retrieve data on UTI index visits from hospital care from Skåne county. We extracted data on day of consultation or days of hospitalisation, diagnosis, antibiotic treatment, urine dip stick, C-reactive protein (CRP) and results from urine cultures. Microbiological analyses had been performed at five different laboratories (one in each county), all using the same approved conventional methods for the identification to the species level .Supplementary material) and an adjacent antibiotic prescription. UTI diagnoses with an antibiotic prescription in the preceding 30 days were excluded. The same patient could be included in the study more than once.We identified eligible patients with a visit in PHC or hospital care, an ICD code indicating lower UTI  and KSH97-P  a short form of ICD-10 adopted to primary care in Sweden .Index visits: A visit to PHC or in hospital with a registered lower UTI diagnosis and a registered prescription of UTI relevant antibiotics on the day of visit or within five days.Antibiotic use: UTI relevant antibiotics within five days from registered visit; the latest prescribed was used in the analysis. Prescribed antibiotics were registered according to the Anatomical Therapeutic Classification System (ATC) [em (ATC) .Study antibiotic: Antibiotics intended to be further compared in the study were divided into three different groups based on previous Swedish treatment guidelines for lower UTI in men concerning broad-spectrum antibiotics and treatment duration  or trimethoprim/sulfamethoxazole ≥10 days) and the present treatment guidelines concerning narrow-spectrum antibiotics .Treatment duration: Number of days of antibiotic treatment noted on the prescription.Therapy failure: A new prescription of a different relevant UTI antibiotic within seven days from index antibiotic prescription and a new registered lower UTI diagnosis.Recurrence: A new visit, a lower UTI diagnosis and an antibiotic prescription (the same day) 8 ≤ d ≤ 30 days from prior antibiotic prescription due to a UTI diagnosis.Complication: A revisit in PHC or hospital care combined with a diagnosis of pyelonephritis or sepsis  and an antibiotic prescription (the same day) within 30 days from the index antibiotic prescription.Microbiology: Bacterial cultures and species determination were performed using approved conventional methods [ methods .The data collected in the study were analysed using Matlab 2019a , Excel 2016 , and SPSS Statistics 25 .Patient characteristics are described as median (IQR) for numerical variables and as numbers and per cent for categorical variables.Comparisons between proportions of categorical variables in two independent groups were performed using the two-sided Chi-square test.Binary logistic regression was used to model the correlation between therapy failure, recurrence and complications and antibiotic choice and other independent variables. Odds ratios (OR) with 95% CI were calculated.p < 0.05 (two-sided).Statistical significance was set at Confidentiality for patients was ensured by using an encrypted ID-number. The study was approved by the Regional Ethical Review Board in Lund, Sweden (Dnr 2016/462).During the investigated years (2012–2015), a total of 44,614 visits diagnosed as lower UTI with a concurrent prescription of antibiotics among men 18–79 years were made in included counties . Of these diagnoses, 22,999 met the study’s inclusion criteria for a correct index visit. In 21,124 of these index visits, antibiotics relevant to this study were prescribed. These visits were eligible for inclusion in the final study .Most patients were handled in PHC (78%). The median age of included patients was 65.0 IQR (51–72) years . Among tE. coli was the predominant bacterium detected in 3529 (30%) of the urine cultures. The second and third most common bacteria were Klebsiella species in 466 (4%) and Enterococcus species in 402 (3%), respectively. In 2066 (18%), other single pathogens were found, and in 805 (7%) of the samples, mixed growth was reported. No bacterial growth was reported in 4387 (38%) of cases. We were not able to retrieve data on antibiotic susceptibility.Urine cultures were retrieved from EMR and matched on day 0 to 5 from index visit. Urine cultures were analysed in 11,655 cases (55%). Urine-dipsticks were positive for nitrite in 34% of analysed samples  and for leukocytes in 74% of samples  .Ciprofloxacin was the most used antibiotic, prescribed in 10,956 cases (52%), followed by pivmecillinam 5234 (25%), and nitrofurantoin 3223 (15%) . For visTherapy failure was registered in 192 (0.9%) and recurrence in 1277 (6%) of the cases . Median Complications within 30 days from index antibiotic prescribing were registered in 121 (0.6%) of cases . Median Therapy failure, recurrence and complications were more common in patients with growth of bacteria in urine as compared with patients with no growth of bacteria, therapy failure 2.67 (95% CI 1.74–4.14), recurrence 2.50 (95% CI 2.1–3.0) and complications 3.87 (95% CI 2.1–7.1). We did not find any association between therapy failure, recurrence and complications in relation to whether urine cultures had been taken or not.p < 0.001) (Therapy failure and recurrence were more common in patients treated with narrow-spectrum antibiotic and trimethoprim (< 0.001) . There w< 0.001) . Older a< 0.001) .There were no significant differences between the incidence of therapy failure, recurrence and complications between Skåne county and the four counties with complete data. The incidence of complications was low for all counties, in Skåne county 0.6% with both narrow- and broad-spectrum antibiotic treatment and for the four complete counties 0.5% with narrow-spectrum antibiotic and 0.6% with broad-spectrum antibiotic treatment.This study included 16,555 men, which were aged 18–79 years with lower UTI in PHC and hospital care, did not show any difference in complication rates between those who received narrow- and broad-spectrum antibiotic treatment. Patients prescribed narrow-spectrum antibiotics and trimethoprim had higher odds of having a reconsultation because of therapy failure and recurrence.This is the first study with the aim to compare treatment outcome between narrow-spectrum and broad-spectrum antibiotic treatment in men with lower UTI. It is also one of few studies on UTI in men that includes over 16,000 patients. Another strength is that we included all men that met the inclusion criteria for UTI in five different counties in Sweden during five consecutive years. We used defined criteria for inclusion, antibiotic prescribing therapy failure, recurrence and complications, which makes the results reproducible. We believe that, despite the lack of an RCT in this area, the findings presented in this study are useful evidence on this topic.Few studies concerning antibiotic treatment and duration of treatment in men have been performed and there are few studies describing the incidence of complications. When planning this study, we estimated that the frequency of complications was 2% based on incidence of complications in women and former studies . Our resA limitation with the study is the retrospective study design. We did not have information about clinical symptoms. Furthermore, we were unaware of how the clinical diagnosis was made, if the patient had a symptomatic UTI or if the UTI diagnosis instead represented a check-up consultation after a former UTI or asymptomatic bacteriuria (ABU). Urine cultures were only performed in 55% of cases. In order to minimise the risk of invalid lower UTI diagnosis, we only included registered index UTI visits with adjacent antibiotics within five days after consultation. We also excluded all cases that had an antibiotic prescription within 30 days prior to the index visit.With age, men acquire structural and functional abnormalities of the urinary tract such as prostatic hyperplasia that can impair normal voiding and can cause UTI . The engWe did not have data on potential risk factors for recurrence and complications such as instrumentation of the urinary tract and comorbidity. No propensity score (matching) was used. Patients that were prescribed ciprofloxacin could have been more affected or more fragile from the beginning (selection bias). We lack information about comorbidities, socioeconomic status, anamnestic factors and actual symptoms that would help to minimise these effects.Data on susceptibility pattern in urine cultures were not possible to retrieve from the EMR. This is a limitation since knowledge about resistance patterns could affect antibiotic choice and outcome.In a retrospective study, Montelin et al.  assessedNo difference between UTI-related hospitalisation and death was seen in a retrospective cohort study with patients aged 65 years and older (27% were men) comparing nitrofurantoin with broad-spectrum antibiotics, although patients prescribed broad-spectrum antibiotics had lower odds of reconsultation and repeat prescription, which is in-line with our study . In a coE. coli [In a large cohort study, which included 22,629 men with UTI aged 18–64 years, antibiotic repeat prescriptions were significantly less likely for UTI episodes treated with trimethoprim than other agents. This is in spite of a higher rate of resistance to trimethoprim in E. coli . This diAccording to the Swedish treatment guidelines for UTI in men, urine culture is always recommended. We find it surprising that cultures were only analysed in 55% of index visits. The reasons behind this are unclear. One of the explanations could be that collecting urine cultures is time consuming and since urine cultures are only collected for special indications in women they are sometimes forgotten in men. Another reason may be that the patients were less affected by the infection, which could make the physicians less prone to order urine cultures. To achieve better adherence to guidelines in men with lower UTI, empiric narrow-spectrum antibiotics should be prescribed, and a urine culture should always be performed. To follow up clinical cure and results from the urine culture, a follow-up contact with the patient should be scheduled. In case of therapy failure, the antibiotic choice should be reconsidered. The low rate of urine cultures is an important finding from the study and a vital issue to address in the future work towards better adherence to guidelines.We did not find any association between therapy failure, recurrence and complications and analysed urine cultures. This phenomenon was also discussed in an article by Ingalsbe et al. . Few uriThe recommended treatment duration for the first-line antibiotics in lower UTI in men (pivmecillinam or nitrofurantoin) is seven days. In our study, median treatment duration for nitrofurantoin was five days, and for pivmecillinam, it was seven days. This indicates that treatment duration differs from treatment guidelines. The minimum duration of antibiotic treatment for lower UTI in men has not yet been determined  but a reComplications within 30 days after a clinical diagnosis of lower UTI in men 18–79 years were rare and there was no difference in incidence of complications among those treated with narrow- and broad-spectrum antibiotics. However, therapy failure and recurrence were more common among patients treated with narrow-spectrum antibiotics and trimethoprim. In spite of higher incidence of therapy failure and recurrence in the narrow-spectrum group, narrow-spectrum antibiotics seems to be a proper first choice antibiotic in male UTI patients, since there is no difference in serious complications such as pyelonephritis and sepsis. Considering the increased rates of drug-related adverse events and the selection of drug-resistant organisms following broad-spectrum antibiotic use, these antibiotics should be preserved for serious infections.Future studies are needed to evaluate the most appropriate antibiotic treatment and duration of therapy for UTI in men.Click here for additional data file.


The elderly need the assistance of walking aids due to deterioration of their physical functions. However, they are often less willing to use these aids because of their worries about how others may think of them. Not using professional walking aids often makes elderly people fall easily when walking. This study explores the behavioral intention factors of middle-aged people (45–64 years old) and elderly people (65 years and older) that affect the use of walking aids. Based on the Theory of Reasoned Action (TRA), subjective norms, attitude toward usage, behavior intention, safety, and usefulness were combined with social image to establish the research framework. This study used questionnaire surveys both in paper form assisted by volunteers and in online electronic form. A total of 457 questionnaires were collected. Data analysis was carried out in three stages: descriptive analysis, measurement model verification, and structural equation model analysis. The results showed that social image had a significant impact on the attitude toward using walking aids. Factors such as attitude toward usage, subjective norms, and safety of walking aids also had a significant positive impact on behavioral intention. Finally, through the research results, some suggestions are proposed for stakeholders to improve the elderly’s concerns about the social image of using walking aids. The world is currently facing a serious aging trend, and the speed of aging is rapidly accelerating. For example, it took 150 years for the population over 60 years old in France to go from 10% to 20%. However, it took only around 20 years for countries such as Brazil, China, and India to reach the same level . In addiAccording to the report, “Taiwan Population Estimates 2018–2065)” , release” , releaThe National Health Interview Survey, conducted by Taiwan’s National Health Administration , interviBecause of the deterioration of the body, many abilities of the elderly are not as good as when they were young, including vision, hearing, balance, reaction time, muscle strength, or endurance. Yang et al. conducted a study on elderly people with mild to moderate difficulties living in institutions . The surTherefore, with age the performance of the elderly in ADLs is most often affected by the ability to walk. Suwannarat et al. conducted interviews and surveys on 343 elderly people over 65 years old in rural Thailand in 2015 . The typSome studies have mentioned that the elderly encounter several major obstacles when using assistive technologies, including privacy violations, insufficient trust in technical assistance tools, lack of value-added features, consideration of purchase costs, and lack of training or embarrassment . RelatedSimpson and Richardson  suggesteIn 2014, the Technology Acceptance Model (TAM) was used to study the technology acceptance of the elderly in Hong Kong  also disTherefore, this research will focus on the factors that influence the behavior of middle-aged (45–64 years old) and elderly (65 years and older) people toward using walking aids in Taiwan. The subjects of the study were not people with severe walking disabilities, but people with mild walking disabilities or those who needed walking supporters because of old age. As Asians live in a closely connected social environment, middle-aged and elderly people are more concerned with social image. Based on the rational behavior theory, the relationship between “social image”, “attitude toward usage”, “subjective norm”, “safety level”, “usefulness”, and “behavior intention” will be verified by a survey investigation. According to the results of this study, it can provide a reference for government agencies and private manufactories to promote walking aids for middle-aged and elderly people.Middle-aged citizens are considered to be those aged 45 to 65 years old, and the elderly those over 65 years old by the Middle-aged and Elderly Employment Promotion Act of the Ministry of Labor  in TaiwaAs the aging population increases, the proportion of people with reduced mobility is also increasing. Koon et al.  pointed In the Assistive Technology Act of the United States, assistive technology is divided into assistive technology equipment (devices) and assistive technology service (service) . AccordiAt present, in the design and research of walking aids, most of them are developed based on the consideration of biomechanics, functional aspect, or appearance ,22,23,24Social image usually plays the role of motivation and cognition. It is a perception that will arouse and imitate real experience in the heart; the feedback obtained after a certain content is disseminated to the public ; and alsIn addition, social image is a topic of concern in care-services-related research fields. Li and Wu  discusseSalifu Yusif et al. reviewed academic journals from 1976 to 2015 and searched 39 articles from Google and Google scholar from 2000 to 2015 . They foSince 2012, Dr. Chang has released conceptual designs of assistive devices that are based on a culturally creative and farsighted technology perspective, thinking about food, clothing, housing, transportation, education, and entertainment shown in  33]. Th. Th33]. Theory of Reasoned Action (TRA) was proposed by Fishbein and Ajzen  to analyConcerning health care and medicine-related fields, for example, the study of organ donation after death  exploredRegarding empirical research on social image and usage attitude, Lin and Bhattacherjee  discusseIn short, for middle-aged and elderly people, the perception of the social image of using a walker will have a positive impact on their attitude toward usage. Similarly, changes in attitudes and subjective norms will also affect the behavioral intention of using walking aids. Therefore, this research proposes the following hypotheses:Hypothesis 1.Social image will have a positive and significant influence on the attitude toward using walking aids.Hypothesis 2.The attitude toward using walking aids will have a positive and significant influence on behavioral intention.Hypothesis 3.Subjective norms will have a positive and significant influence on the behavioral intention of using walking aids.The safety aspect refers to safety awareness, which means whether people can be aware of their own safety . The higIn addition, safety needs to be considered in the research on intelligent nursing aids. For example, Kwee-Meier, Bützler, and Schlick  found inAll in all, the perceived security level has a positive effect on behavioral intentions. For the elderly, the higher the perceived safety, the higher their intention to use walking aids. Therefore, this research infers that the perception of the middle-aged and elderly of the safety level has a positive and significant impact on behavioral intentions. The proposed hypothesis is:Hypothesis 4.The perceived safety level of walking aids will positively and significantly affect the behavioral intention of using walking aids.Fred Davis  proposedThere are many related studies. For example, Lin and Chang  studied In summary, usefulness has a positive effect on behavioral intentions. For users of walking aids, the higher the perceived usefulness, the higher will be their behavioral intention to use the aids. Therefore, the proposed hypothesis is:Hypothesis 5.The usefulness of walking aids will positively and significantly affect the user’s behavioral intentions.In the applied research on social image and usage attitude, Lin and Schlick  verifiedBased on the above research, social image has a positive influence on usage attitude, and usage attitude has a positive influence on behavior intention. For the user of walking aids, the more positive the social image of using walking aids is, the more positive the attitude toward using aids will be. Therefore, this study infers that middle-aged and elderly people’s social image perception of using walking aids will have a positive and significant impact on behavioral intentions through their attitudes. The proposed hypothesis is:Hypothesis 6.The attitude toward the usage of walking aids has a mediation effect between social image and behavioral intention.This research explores the behavioral intentions of the middle-aged and the elderly toward the use of walking aids and studies the influencing factors. This study took social image, usage attitude, subjective norms, safety level, and usefulness as independent variables. Among them, usage attitude also played the role of a mediating variable. Behavioral intention was the dependent variable. Through the literature review, the research model is drawn as shown in This study explored the intention of middle-aged and elderly people to use walking aids, so the research subjects were people over 45 years old. This research used questionnaires, which were conducted online and in the form of paper, which was assisted by volunteers. In the north, middle, south, and east of Taiwan, we collected research data through community elderly associations, religious groups, civil organizations, and assistive device manufacturers. The questionnaire collection period of time was from 1 May 2020 to 30 June 2020. After deleting invalid questionnaires, there were a total of 406 valid questionnaires. According to the sample size requirement formula from the survey system website , when thThe research questionnaire included the investigation of the basic participants’ background information and their opinions of the research constructs. The background information, including gender, age, education, marital status, occupation, family environment, and residential area, was investigated in the first part of the questionnaire. Then, in the second part of the questionnaire the six latent variables were measured by a Likert seven-point scale ranging from “strongly disagree” (1) to “strongly agree” (7). The measurement items were mainly adapted from the previous studies. All items were originally written in Chinese and modified to the suitable walking aids usage scenario for the survey participants. First, there were five items related to users’ attitudes toward using walking aids. Three items were adapted from Wu and Lin’s study , one iteThe results were processed in three sections: descriptive statistical analysis, measurement model verification, and structural equation modeling analysis. In this study, the structural equation model (SEM) was used to obtain the relevant conclusions. The Likert seven-point scale used in the questionnaire was a continuous scale, which is statistically consistent with a normal distribution and obtains relatively accurate results. However, some of the research variables in this study were nominal scales, such as gender, marriage, or occupation. These variables could not be analyzed using structural equations, which limit the results of the research ,71,72. DThe categorical data elements of the 406 valid questionnaires included gender, age, education, marital status, occupation, family environment, and residential area. The respondents were 70.2% female. Most of respondents were aged 45–64, which was the definition of middle-aged people. A total of 45.32% of the respondents were aged between 45 and 54, and 39.66% of respondents were aged between 55 and 64. Regarding the education level, the largest group was college and university, which was 47.04%. A total of 361 respondents were married, which was 88.92%. The data are shown in p < 0.05). It meant that age made a significant difference in the social image construct. After comparing with the Scheffe method, it was found that subjects 55–64 years old had a significantly higher opinion in the social image construct than those 45–54 years old, and subjects 65 years or above had a significantly higher opinion in social image than those 45–54 years old. The testing results are shown in The F-test of different ages in the social image construct reached a significant level , combined with the social image and attitude toward usage as mediating variables, the research framework and related hypotheses were proposed. After collecting data through a questionnaire survey, the structural equation model was used to test the model and verify related hypotheses. Based on the Theory of Reasoned Action (TRA), this research attempted to explore the factors affecting the behavior of middle-aged and elderly users from the perspective of social image. Therefore, integrating factors such as safety, usefulness, and social image dimensions were used to discuss the influence on middle-aged and elderly people’s intention to use walking aids. The research results are as follows.The results of the study showed that social image has a significant positive impact on attitudes toward using walking aids. This result was consistent with the previous research . The aveIn the path analysis of the influence of social image on use attitude, the non-standardized regression coefficient reached 0.243, indicating that social image factors had a high proportion of influence on use attitude. It also confirms the hypothesis of this study that social image has a significant influence on the attitude toward using walking aids. Therefore, it is also proved that middle-aged and elderly users are obviously concerned about the social impression of disability, aging, and the dependence caused by the use of walking aids. This differs from ordinary people, so it affects their attitude toward using mobility aids. At the same time, if they were to choose a more advanced walker, whether it was for a change in function or appearance, it would not enhance the attitude toward using a walker.The results of this study showed that the attitude toward using walking aids has a significant positive effect on behavioral intentions. This result was similar to the results of previous studies . In addiIn the attitude toward usage construct, a positive view appeared, which meant that users agree that if their walking function was affected in the future, they would be open and willing to accept using walkers. The behavioral intention construct reached the highest average score of 6.324, indicating that if having difficulty walking in the future, the participants would use walking aids to assist walking, and even to convey positive messages or to recommend it to others. The subjective norm item “I will try to use it because the professional recommended the benefits of walking aids” gained the highest average score, 6.36, and its standard deviation value was 0.77. That means not only high agreement among the participants on this question, but also that as long as the use of walking aids is recommended by professionals, the user’s willingness to use it will be greatly increased.The intensity of the perception of safety has a significant impact on the behavioral intention of using walking aids. This result was similar to the results of previous studies ,47. In aFor users, the average score of the safety aspect was 5.838, which meant that they are less worried about the safety of walking aids. At the same time, in the safety construct, the non-standardized regression coefficient of behavioral intention reached 0.283. In addition to being an important influencing factor on the behavioral intention of using walking aids, it also meant that after users feel that safety is guaranteed, their willingness to use walking aids will increase significantly. In addition, the score of related items in usefulness also reached 6.01, and standard deviation was 0.85, indicating that users agree that walking aids are useful. However, since the regression coefficient was 0.178, the lowest of all factors, the degree it affected the behavioral intention of using walking aids was not so obvious.Social image affects the attitude toward usage, and the attitude toward usage significantly positively affects the behavior intention, that is, the social image of using walking aids indirectly affects the behavioral intention. The attitude toward usage had a mediating effect, and this result was similar to the previous studies ,42. It cThe World Health Organization (WHO) proposed the Global Aging and Health Strategy and Action Plan in 2016 , which mTaiwan began to implement National Ten-year Long-term Care Plan in 2008, providing assistive equipment and barrier-free environment improvement subsidies, including crutches, walking aids, or walkers. In 2018, the National Ten-year Long-term Care Plan 2.0 was promoted , and theAs many elderly people get older, the function of their lower limbs deteriorates, which affects their walking function. However, they are afraid of being laughed at, their external image becoming morbid or weak. This may be why the middle-aged and elderly are reluctant to use walking aids. Instead, they will walk with umbrellas or bamboo poles, which is not only very laborious but also prone to danger. Therefore, it is very important to understand the influence of “social image” on users for the research on the use of walking aids by middle-aged and elderly people. In the past, research on assistive devices mostly focused on the design of the mechanics, functional aspects, and appearance of walking assistive devices. The behavior of assistive devices from the perspective of the user’s mentality and the relationship between related influencing variables were rarely studied.Therefore, improving life functions through assistive devices is very important in an aging society. According to the present study, for these middle-aged or elderly people who are facing gradual degradation of functions, if the use of assistive devices cannot overcome the existing poor social image, no matter how sophisticated the assistive device is, it still cannot increase the willingness to use it. The group between the ages of 45–55, especially, was more concerned with social image than other elderly groups. It also becomes impossible to use assistive devices to achieve social participation, thereby delaying aging and increasing physical and mental health.This study mainly sampled the middle-aged and elderly people in the urban area. The results of the study indicated that the sampled subjects had relatively high academic qualifications; a college degree or above accounted for 74.4%. However, the higher the level of education, the higher the ability to absorb information about assistive devices, and the higher the proportion of self-help ability in understanding the use of assistive devices. This study may not be able to fully present the attitudes and intentions of other people with lower academic qualifications. In addition, the majority of the subjects were under 65 years old (85%), and the elderly group sample (65 years old or above) was relatively small. Future research can improve in the sampling process. In addition, this research focuses on walking aids. In the future, research can focus on the intention of using other types of assistive devices, such as wheelchairs, hearing aids, or visual-impairment-related assistive devices, providing more about the use of various assistive devices.


Clostridioides difficile infections (CDI) is post-antibiotic intestinal dysbiosis. CDI affects both ambulatory and hospital patients. Aim: The objective of the study was to analyze the possibility of utilizing databases from the European Centre for Disease Prevention and Control subject to surveillance for the purpose of identifying areas that require intervention with respect to public health. Methods: The analysis encompassed data concerning CDI incidence and antibiotic consumption expressed as defined daily doses (DDD) and quality indicators for antimicrobial-consumption involving both ambulatory and hospital patients in 2016. Results: In 2016, in the European Union countries, total antibiotic consumption in hospital and outpatient treatment amounted to 20.4 DDD ; in ambulatory treatment using average of ten times more antibiotics than hospitals. In total, 44.9% of antibiotics used in outpatient procedures were broad-spectrum antibiotics. We have found a significant relationship between the quality of antibiotics and their consumption: The more broad-spectrum antibiotics prescribed, the higher the sales of antibiotics both in the community sector and in total. CDI incidence did not statistically significantly correlate with the remaining factors analyzed on a country-wide level. Conclusion: Antibiotic consumption and the CDI incidence may depend on many national variables associated with local systems of healthcare organization and financing. Their interpretation in international comparisons does not give clear-cut answers and requires caution.Background: The most important pathomechanism of  Clostridioides difficile is the most significant pathogen responsible for antibiotic-related diarrhea, and the most critical exposure factor is the consumption of antibiotics that disrupt the gut microbiota [Clostridioides difficile infections (CDI) are clindamycin, beta-lactams and fluoroquinolones [crobiota . The antinolones . CDI mayinolones . Hyperviinolones . Strain inolones . It shouinolones  and in Pinolones .Antibiotic Stewardship Program is, on the one hand, application of data on CDI incidence as a measure of exposure to CDI, and on the other hand, monitoring antibiotic use as measured by the Defined Daily Dose (DDD)—a technical unit of measurement of drug consumption, defined by the World Health Organization (WHO) [Antibiotic stewardship limits exposure to CDI in hospitals; hence, according to Barlam et al., one of the elements of the on (WHO) ,9. Many on (WHO) , confirmIndicators to measure the quality of antimicrobial stewardship in primary care and, secondly, in hospitals were developed and validated by the European Surveillance of Antimicrobial Consumption program . One of The objective of the study was to analyze the possibility of utilizing aggregate data concerning CDI incidence and antibiotic consumption at the national level, for the purpose of identifying areas that require intervention at the level of public health.The statistical analysis was prepared, using publicly available data from the European Centre for Disease Prevention and Control for 2016:1. Concerning antibiotic consumption based on:a. Antimicrobial consumption database (ESAC-Net), fluoroquinolones, beta lactams, macrolides, lincosamides and streptogramins expressed as DDD per 1000 inhabitants and per day were taken into consideration, the DDD is defined as the assumed average maintenance dose per day for a drug used for its main indication in adults.https://ecdc.europa.eu/en/antimicrobial-consumption/database/rates-country, https://www.ecdc.europa.eu/en/antimicrobial-consumption/database/qualityindicators).b. The Quality indicator for antibiotic consumption in the community according to ECDC methodology was defined as the ratio of the consumption of broad-spectrum antibiotic (J01(CR+DC+DD+(F-FA01))) to the consumption of narrow-spectrum antibiotic (J01(CE+DB+FA01)); consumption of antibiotics was compared for hospitals and outpatient care; data from The European Surveillance System—TESSy, provided by  and released by ECDC , in 71.5% hospital surveillance periods, the reported diagnostic practices followed ESCMID recommendations .Quantitative evaluation of the measured variables employed basic statistical measures, i.e., mean, standard deviation, and minimum and maximum values. In order to verify the statistical significance of relationships between antibiotic consumption in ambulatory and hospital care expressed in DDD (defined daily dose) per 1000 inhabitants and per day and CDI incidence and/or incidence density in 2016, Pearson’s correlation coefficients were used. The selection of parametric significance tests was dictated by the fact that the measured variables have probability density distributions converging to the Gaussian distribution. In order to determine the predictive model with 95% confidence, the least squares model was developed. These models were done for variables exhibiting significant correlations, i.e., community and total consumption of antibacterials  for systemic use in the hospital/community sector and consumption of other beta-lactam antibacterials (ATC group J01D) for systemic use in the hospital/community sector. All statistical tests were calculated at 95% statistical confidence interval, i.e., at the level of significance of alpha = 0.05.The mean antibiotic consumption involving in-hospital and ambulatory treatment amounted to 20.4 DDD ; outpatient care employed 10 times more antibiotics than hospitals: 18.6 DDD vs. 1.9 DDD. Discrepancies between in-hospital and ambulatory antibiotic usage were 9.8 times higher: 18.6 DDD vs. 1.9 DDD, the discrepancy was particularly high for lincosamides and streptogramins (ATC group J01F): 20.3 times more: 3.04 DDD (ambulatory) vs. 0.15 DDD  . This obp < 0.001). The more broad-spectrum antibiotics, other beta-lactams (ATC group J01D) for systemic use prescribed, the higher the sales of antibiotics both in total  and in community sector   .Mean CDI incidence density was 4.6 cases/10,000 patient-days (pds), higher in hospital sector than in community: 3.7 vs. 0.9. CDI incidence, both in total and divided into HA-CDI vs. CA-CDI, did not statistically significantly correlate with the remaining factors analyzed. p = 0.053) between hospital use of “other beta-lactams” and HA-CDI—as expected, this class includes carbapenems, which are the single highest group of antibiotics conferring CDI risk  .One of the strongest CDI predictors is the use of antibiotics. This is confirmed by the present data in relation to Poland, in which both antibiotic consumption and CDI incidence were among the highest and the latter was more than two times higher than the average for Europe: 7.6 vs. 3.2/10,000 pds. Unfortunately, in Poland, in 2007–2016, outpatient care saw a significant increase in the total sales of antibiotics, by 8.3%; it was also true for the consumption of the group of antibiotics whose relationship with CDI is the strongest, i.e., fluoroquinolones, by 13.5% [In hospital care, the departments with particularly high antibiotic consumption are intensive care units (ICUs). A single-center study from a Polish ICU, in which the consumption of antibiotics amounted to a very high level of 1913 DDD/1000 pds, with an alarming CDI incidence, 10.6/10,000 pds, and additionally a simultaneous exceptionally high and disturbing prevalence of high-resistance strains was found . HoweverOther departments in which CDI poses a problem are surgical wards, where, on the one hand, perioperative antibiotic prophylaxis is applied, including, e.g., fluoroquinolones in urology, and in the treatment of healthcare-associated infections, including surgical site infections, broad-spectrum antibiotics are used . AccordiOne of the elements of a comprehensive program of antibiotic management at the hospital level is the evaluation of their consumption and cost analysis covering both the costs of purchasing and administering the antibiotic and the remaining infection treatment costs ,22. ManyRegardless of the problem of research methodology limitations indicated in this study, the introduction of a sensible antibiotic policy in many of the countries studied seems to be a necessity. For Polish hospitals, it might prove to be a considerable challenge. Poland, as one of the Central and Eastern European countries, represents an example of a poorly functioning epidemiological surveillance system, which was demonstrated by Ider et al. on the example of healthcare-associated infection (HAI) surveillance, since in the countries of the post-Soviet bloc, there is a problem of weak commitment and insufficient resources, especially regarding the staff, lack of specialist knowledge and unsatisfactory publication of data on HAI epidemiology .The present data indicate that interventions concerning surveillance of antibiotic consumption have to encompass not only hospitals but also physicians in outpatient care, since a significant portion of the antibiotic market involves ambulatory patients ; in PolaThe 2016 CDI data of HAI-Net are not fully representative; the collection of incidence data on CDI at European level started on 1 January 2016. Several countries have not submitted data at all  or data from 1–4 hospitals only . Some countries have submitted data from a larger number of hospitals . The ESAC-Net, the source of data on antibiotic consumption, has been running for many years now; it is a well-established surveillance. Due to the above issue, no valid conclusions can be derived directly from the comparative results of the study (antibiotic consumption vs. CDI incidence).Antibiotic consumption and the CDI incidence may depend on many national variables associated with local systems of healthcare organization and financing. Their interpretation in international comparisons requires caution. It is also a confirmation that looking for solutions to problems as universal as CDI prevention and control necessitates detailed descriptions of the local situation and taking into account local conditions and limitations. Aggregate data concerning antibiotic consumption at the national level do not lend themselves to detailed analyses as regards CDI.


The main weakness of the technology is the interface strength between the extruded layers, which are deposited at different time intervals. Consequently, the interface strength is assumed to vary in relation to the time of concrete casting. The proposed experimental study investigated the behavior of a hardened concrete mixture containing coarse aggregates that were up to 8 mm in size, which is rather unusual for 3DCP technology. The resulting direct tensile strength at the layer interface was investigated for various time intervals of deposition from the initial mixing of concrete components. To better understand the material behavior at the layer interface area, computed tomography (CT) scanning was conducted, where the volumetric and area analysis enabled validation of the pore size and count distribution in accordance with the layer deposition process. The analyzed CT data related the macroscopic anisotropy and the resulting crack pattern to the temporal and spatial variability that is inherent to the additive manufacturing process at construction scales while providing additional insights into the porosity formation during the extrusion of the cementitious composite. The observed results contribute to previous investigations in this field by demonstrating the causal relationships, namely, how the interface strength development is determined by time, deposition process, and pore size distribution. Moreover, in regard to the printability of the proposed coarse aggregate mixture, the specific time interval is presented and its interplay with interface roughness and porosity is discussed.  Digitalization in the construction industry could be perceived as being at an early birth stage, despite earlier attempts to develop robotic construction systems .2 emissions production is due to the construction industry. The main aim of additive manufacturing (AM) is to quantitatively minimize this impact on the environment and loss of life on the construction site [The correlation between productivity growth and the digitalization index is well known; therefore, it is no surprise that the construction sector has a lower digital index, with productivity growth localization being in negative values. Currently, for example, one-third of the world’s energy consumption and COAM used in the construction industry, called 3D concrete printing technology (3DCP), has developed rapidly in recent years. While being more experimental than general, it is already used for the construction of small-sized buildings, complex-shaped prefabricated concrete elements, and constructions without requiring the use of expensive formwork. However, this technology has several issues that have not yet been fully resolved, though autonomous construction systems have the potential to improve the speed, quality, and safety of the onsite fabrication of architectural-scale structures under various environmental conditions .As the principle of 3DCP technology consists of concrete layering over time intervals, one of the major issues is the interface strength between adjacent layers. However, it is important to point out that once a very short time interval passes, the bearing capacity of an extruded concrete layer is not high enough to withstand the dead load resulting from layers cast on top of it. Moreover, the adhesion quality worsens with the increasing length of the print-time interval . ConsequThere are a few experimental studies that have dealt with the effects of the print-time interval on the adhesion strength of 3D-printed concrete layers. One of these studies  focused Using a different approach, Rubio et al. demonstrated that printed mortars exhibited improved mechanical behavior compared with cast specimens. This was due to extrusion, which has a positive effect on the density of the mortar because of the fast layering process that hides defects, though this process does not enable the creation of cold joints . Note thBoth studies investigated the interface strength between extruded concrete layers with respect to different boundary conditions. As the experiments were conducted on cement-based composites with only fine aggregates, the presented experimental investigation was proposed with the aim of observing the interface strength of concrete with coarse aggregates in the form of crushed stone with a maximum nominal size of 8 mm, which is used only rarely at present for 3D concrete printing technology ,12. BasePortland cement concrete that was suitable as material available for use in AM and formed using 3DCP was manufactured during this project. The key mechanical requirement of a cement-based composite was a high strength that is sufficient to withstand compressive stress during early formation (grades of cement as per European Standard–EN-197-1).400 kg Portland cement (OPC) conforming to the European standard, strength class 42.5 R;1130 kg fine aggregate 0–4 mm;300 kg coarse aggregate—crushed stone 4–8 mm;100 kg Metakaolin, Mefisto L05, České Lupovské závody, Pecínov, CR, Czechia;3 kg liquid solidification accelerator, Betodur A1, Stachema, Kolín, CR, Czechia;285 kg of water.The proposed concrete composition was as follows (mass per one cubic meter):Cement-based composites for 3D printing technology should be adapted mainly to meet requirements for fresh concrete, such as in terms of extrudability and buildability. These properties are mutually related to the workability and open time of a fresh mixture. Prior to the concrete production, the relative humidity and temperature of each concrete component were measured .The initial setting time of the cement paste consisting of cement, water, liquid solidification accelerator, and Metakaolin was intended to define a time frame in which it was possible to print using the concrete mixture. However, as the Vicat apparatus test was not developed particularly for 3D concrete printing, an extrusion-based test focused on the quality control of the deposited concrete layers was also performed.The components of the mixture  were dry-mixed for about 2 min. Then, tap water with liquid solidification accelerator Stachema Betodur A5 was added immediately, and mixing was continued for about 2 min. After mixing, the mixture was homogenous and formed into a consistent fresh state . Subsequently, a concrete slump test was undertaken to observe the workability of the proposed fresh mixture.The main objective of the extrusion-based test was to print single concrete layers at various elapsed times from the initial mixing of the concrete components and to subsequently control the quality of the deposited layers visually. The layers were extruded using a specially designed extruder  at a conBased on the obtained findings, the so-called open time was determined, which defines a time in which the fresh concrete is still workable enough for 3D printing technology. The best quality of extrusion was obtained in the open time from 20 to 40 min. Once the open time was determined, 20 concrete specimens were prepared from 4 fabricated specimens for the uniaxial tension test. First, the concrete mixture was deposited into the form mid-height (25 mm) 20 min after the initial mixing of concrete components. Second, the other layers were deposited at five-minute intervals into the 50-mm-high form, and the formwork was then covered with cling film in order to avoid moisture loss. After 28 days, the whole concrete elements were cut into 24 concrete specimens. Twenty specimens were bonded to steel plates using epoxy glue to measure the interface strength, and 4 specimens were used for computed tomography (CT) analysis to analyze the porosity and distribution of the coarse aggregate.All parameters were retained for repeatability with print tracks using 3DCP.The Vicat apparatus test was performed on the cement paste with the aim of observing the setting time of the proposed mixture to determine for how long the concrete mixture might be workable enough for 3DCP. First, it was necessary to find the adequate content of mixing water required to produce the normal consistency of a cement-based mixture, which was subsequently used for determining the setting time in accordance with EN 196-3. The mixture was composed of cement and Metakaolin was used as a partial cement replacement. Subsequently, the mixture was used for observing the initial setting time and final setting time in accordance with the same standard .The principle of assessing the extrudability involved setting the exact time interval after the mixing process in which to print single layers. Time intervals of 5 min were used, followed by subsequent visual observation to assess the print quality. Note that the same method was used in a study by Ma et al., where the findings show that with good extrusion of the mixture, violation of the continuity of the printed trace in the form of cracks was eliminated .Z-axis direction using a trowel to demonstrate the sliding of the nozzle during the 3DCP process . This scanning apparatus was used for assessing the real area of the layer interface to determine the exact dimensions. Analytical software GOM Inspect 2018  was used to obtain more accurate specimen dimensions, especially for the real area of the layer interface . The priUniaxial tests were conducted to measure the interface strength. Note that which testing method to use to determine the interface strength of the printed concrete is still an open question.3 into twenty specimens with dimensions of 50 × 40 × 150 mm3. The cross-section of concrete blocks (40 × 50 mm2) was selected to simulate two concrete layers produced using 3D concrete printing technology with nozzle dimensions of 25 × 40 mm2. Subsequently, steel T-profiles were glued to the top and bottom of each block with the epoxy glue Sikadur-31 EF  with a tensile strength of 20 N/mm2 after 3 days of drying at a temperature of +23 °C [It was necessary to cut four initial precast concrete elements with dimensions of 50 × 40 × 1250 mmf +23 °C .Attention was paid to accurately align the specimens in the machine to obtain pure tension and avoid eccentricity that would distort the results.The uniaxial tension tests were performed on the prepared specimens with the aim of observing how the interface strength varied with respect to the time interval between the printing of two adjacent concrete layers.F and A are the applied tensile force and nominal cross-section area of the specimens, respectively:The tests were conducted with a displacement rate of 1 mm/min in a Zwick Materialprufüng Z020 device with a 20 kN load cell . The obtThe last four specimens were visualized using computed tomography . The main parameters of the X-ray tube were a voltage of 180 kV, current of 200 µA, and a 0.5 mm thin copper plate filter. The measurement was focused only on the selected region , which aThe software analyses aimed to determine the porosity ratio and distribution of the cement-based composite. Both ratios were calculated using a thresholding algorithm for determining the boundary between the materials. The threshold used for porosity detection was determined automatically by the software according to peaks of the data histogram representing the air (background) and other materials for better comparability of the results. Only the closed pores  were considered in the analysis results. Since the histogram did not allow one to clearly identify different materials in the specimen, the threshold used for white cement-based composite detection was selected by the operator individually for each specimen according to visual inspection in representative cross-sections. Because the cement-based composite was not completely homogenous, the results reached by the thresholding approach were optimized using the erode/dilate function. Cement-based composites were captured in the data as regions of interest. Their distribution was then expressed as a proportion of the region volume to the whole specimen volume.The interface force should have the same trend as described in the study by Le et al.  and SanjThe interface strength is affected by the number of pores and their sizes, in addition to interface roughness, which depends on the aggregate size and type of material used. Concrete elements that are 3D-printed out of aggregate particles are supposed to fail at the layer interface when the strength of the cement paste matrix is exceeded.During the process of the deposition of a material with a higher fraction of coarse aggregate, there is a probability that the roughness of the first-layer surface could cause air bubble locking due to the deposition of a second layer. The assumption is that with a large time gap, a large number of pores would be observed at the interface area close to the coarse aggregate grains.The main objectives of the study were to analyze the tensile strength at the interface of the 3D-printed concrete layers and to validate three main hypotheses formulated in the scientific literature:The experimental data obtained from the Vicat test were used for the elaboration of the graph presented in The operating assumption of the Vicat apparatus test was verified using the extrusion-based test when investigating the extrudability of the mixture, where the gathered data show a partial relation between the results from the Vicat apparatus test and the extrusion-based test’s optimal open time.The principle of the test was to print single layers in time interval spans of 5 min ranging from 10 to 65 min, as counted from after the mixing was finished, and to subsequently visually observe the layer quality. The obtained findings demonstrate that the layer extruded 10 min from the initial mixing of components was not able to retain its shape due to the very fluid consistency of the concrete. In contrast, the layers extruded later than 40 min from the initial mixing of components showed shape discontinuity and minor cracks that likely resulted from the concrete consistency being too viscous. Consequently, the optimal print time of the proposed concrete mixture was between 20 and 40 min from the initial mixing of concrete components . Note thWhile the number of cracks in the extruded layers was not affected by the age of the cementitious composite too much, the width of the cracks rapidly increased with increasing time. In particular, the crack width was equal to 0.3 mm and nearly 1 mm at the time 45 min and 65 min, respectively. However, it is important to point out that only a visual check was conducted and a deep investigation of this phenomenon should be carried out in the future.For the deposition of concrete, the forms and trowel with adjustable heights were built . The dep2 was not required [Each specimen was optically scanned after being cut off from the concrete element. The optical properties (surface matt and reflection) meant that the specimens were suitable for direct scanning, where coating of the surface with TiOrequired . The bouThe interface strength was based on the equation of engineering stress (Equation (1)). The results from the proposed experiment demonstrated the assumption about the relation between the adhesion strength and time interval between the deposition of concrete layers. It was evident that the interface tensile strength gradually decreased from 2.6 to 2.1 MPa as the time interval increased. This investigation also showed that the time interval between the deposition of concrete layers affected the failure mode of the test specimens.The probability of specimen failure in the interface area was the most significant when using a delay time of 20 min with a 100% failure rate, then 15 min with an 80% failure rate, 10 min with a 40% failure rate, and 5 min with a 20% failure rate.The values show that the interface strength of the deposited layers was significantly influenced by the delay time used for the layer deposition. The interface strength was strong at 5 min, and from this delay time, there was a decreasing trend between specimens deposited at 10 and 15 min, where a small fluctuation was measured . A similThe failure area of all the specimens was not smooth, as is typical in fine-grained concrete mixtures . The craThe interface area, where the old and new concrete mixtures interact, can be considered as a thin layer consisting of very fine particles. This thin film is usually localized on the outer surface of the fresh mixture and functions as a lubricant between the mixture and pipe during the pumping process. The results in this study confirmed the explanation of the results from the study of Panda et al., where they explained the differences between the roughness on interface surfaces that were deposited/3D-printed at different times. The roughness decreased with the time delay interval, which correlated with the drying of the thin-film layer. This means that the thin-film layer diminished and the adhesion of the layers was no longer efficient . The autIn the direct tensile test of the specimens, two kinds of crack patterns were observed: the first kind of pattern a was chaThe geometric shape of the pores and their size and distribution within the whole volume directly affects the concrete strength and its durability due to their influence on the action of forces. The pore structures inside a concrete mass are very complex and have variable size scale distributions. The size of pores ranges from the nanoscale to millimeter size, while the majority of pores are formed as a result of the mixing process and evaporation of excess water ,22.0.5–10 nm gel pores10 nm–10 µm capillary pores50 µm–1 mm air pores.The size of pores can be sorted into three basic categories according to their relative diameters:As seen in the specimen failure detail a,b, highFor the CT, the resolution of 38 µm was set according to the size of the specimens and the relevant size of pores based on previous studies. The size recognition of pores is dependent on the resolution and went from 50 µm to several millimeters. The volume analysis showed that the defect volume ratio had different results for each specimen , but witThe bottom layer of the T20 specimen was hardened enough and much less affected by the compressive force from the upper layer. This allowed us to observe the effect of moisture inside each layer structure. The area analysis of the air pore distribution  providedIn summary, this experimental study was proposed with the aim of observing the influence of the time interval between casting concrete layers on the tensile strength at their interface. Two-layer concrete elements with different layer deposition times were manufactured, with etalon used as a measure for the extrusion-based 3DCP. The mix composition was the same during all experiments. The results from the uniaxial tension test enabled us to draw the following conclusions. (1)The results supported the first hypothesis and the assumption about the development of interface strength in relation to the time interval between the casting of concrete layers. The interface strength decreased with an increasing time interval. This matched a study by Panda et al., where a similar trend was observed . This alIn addition, Rubio et al. conducted a study in which printed mortars exhibited improved mechanical behavior compared with cast specimens. This was due to extrusion, which has a positive effect on the density of the mortar because of the fast layering process that hides defects, though this process does not enable the creation of cold joints. The study found that heterogeneity was induced by 3D printing through extrusion/deposition on dense mortars. The density of the upper layers was lower than that of the bottom layers after the deposition/printing. This means that lower layers were consolidated. This phenomenon of consolidation has a direct impact on resistance levels . Note th(2)The geometric shape of the pores and their size and distribution within the whole volume directly affects the concrete strength and its durability by influencing the action of forces . During (3)Based on the first and second hypotheses concerning the deposition process, Van Der Putten et al. concluded that increasing the time delay to deposition induces a higher number of bigger pores in the lower and central parts of a specimen . This wa(1)Based on previous studies, the interface strength is related to the roughness of the surface, pore size, and thickness of a thin film of very fine particles . The siz(2)The propagation of cracks was proven to be related to the homogeneous arrangement of pores and aggregate (distribution and size) throughout the specimen, which was related to the effect of moisture and pore migration depending on the setting stage of the concrete.(3)Regarding the test specimens in which the material was layered 20 min after mixing, the layers did not bond perfectly due to solidification. This resulted in inhomogeneity of the pores throughout the specimen and, thus, inhomogeneous overall hardness. In the direct tensile test, these specimens were broken exactly at the layer interface.(4)The results obtained from the extrusion-based test performed within the scope of the work demonstrated that it was possible to print from the proposed mixture within 20 to 40 min of the initial mixing of concrete components, and the results obtained from uniaxial tension testing indicated that layer deposition was appropriate for 3DCP in terms of good adhesion between layers within a time interval from 5 to 10–15 min.(5)In the case of 3DCP, the lower interface strength was predicted on the basis of the volume ratio and area ratio of porosity, and the stress concentration that occurred during the 3DCP process in the layer deposition. This determined the crack pattern and specific specimen failure .It is necessary to highlight that the correlation between the time delay of deposition and interface strength was established for the specific defined material and specific surface conditions. This study established a basic etalon measure to determine the interlayer strength with 3DCP and formwork technology. It is necessary to investigate the influence of surface conditions of the contact surfaces between layers on the interface strength for 3DCP for every mixture.