Bacteria have evolved to develop multiple strategies for antibiotic resistance by effectively reducing intracellular antibiotic concentrations or antibiotic binding affinities, but the role of cell morphology in antibiotic resistance remains poorly understood. By analyzing cell morphological data for different bacterial species under antibiotic stress, we find that bacteria increase or decrease the cell surface-to-volume ratio depending on the antibiotic target. Using quantitative modeling, we show that by reducing the surface-to-volume ratio, bacteria can effectively reduce the intracellular antibiotic concentration by decreasing antibiotic influx. The model further predicts that bacteria can increase the surface-to-volume ratio to induce the dilution of membrane-targeting antibiotics, in agreement with experimental data. Using a whole-cell model for the regulation of cell shape and growth by antibiotics, we predict shape transformations that bacteria can utilize to increase their fitness in the presence of antibiotics. We conclude by discussing additional pathways for antibiotic resistance that may act in synergy with shape-induced resistance. Antibiotic resistance is one of the major threats to human society. It has been estimated that each year, 700,000 people die as a consequence of infections caused by resistant bacteria, prompting an urgent response in order to prevent devastating global effects within generations . To undeS/V), or curvature  and to decrease S/V in nutrient-poor media (to inhibit antibiotic influx). We conclude by discussing additional mechanisms of countering antibiotics via regulating metabolic pathways and membrane porin and efflux pump expression that may act in synergy with shape-induced resistance.Changes in cell size and shape can be physiologically beneficial to antibiotic-treated bacteria in several ways. An increase in the cell volume can dilute the antibiotic concentration inside a cell, thereby promoting cell growth. A reduction in the cell . An incrc influx . The modibiotics , in agreibiotics . To undeE. coli cells treated with 42 different antibiotics belonging to 5 different categories based on their binding targets   , and an erulenin . We findriclosan . For theenvelope , 26, S/Vibiotics  22). Wh. WhE. coe efflux  as well 10.1128/mbio.00659-22.2FIG S1E. coli cells under treatment with different antibiotics. (A) Cell surface area represented with color as a function of the cell width and cell aspect ratio. Red represents an increase and blue represents a decrease in the surface area relative to untreated cells. The black dashed line represents a constant surface area as measured for untreated cells. (B) Cell volume represented with color as a function of the cell width and aspect ratio. The dashed black line represents a constant volume as measured for untreated cells. Download FIG S1, EPS file, 2.2 MB.Surface area and volume of Copyright © 2022 Ojkic et al.2022Ojkic et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the ain, and the substrate concentration, x, are given byaout is the concentration of the antibiotic in the extracellular medium, x0 is the substrate concentration in the absence of the antibiotic, xk is the rate of substrate production, kon is the rate of binding of the antibiotic to the substrate, koff is the antibiotic unbinding rate, and Pin and Pout are the membrane permeability coefficients in the inward and outward directions, respectively. The last term on the right-hand side of k is the bacterial growth rate. Using model parameters provided in S/V predicts the time evolution of the intracellular antibiotic concentration  − kaindxdt = kxntration , where tion  mathematical model for intracellular antibiotic dynamics, (2) mathematical model for the dynamics of membrane-targeting antibiotics, (3) single-cell growth and shape dynamics under treatment with ribosome-targeting antibiotics, and (4) simulation protocol and choice of model parameters. Download Copyright © 2022 Ojkic et al.2022Ojkic et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the S/V upon antibiotic treatment  relative to the extracellular concentration, as S/V is varied between a chosen minimum, (S/V)min, and a maximum value, (S/V)max. The dilution factor is thus dependent on the variation in S/V, growth rate k, influx permeability Pin, and outflux permeability Pout max and (S/V)min are taken to be the surface-to-volume ratios for the untreated cell and the antibiotic-treated cell, respectively. Similarly, meropenem-treated A. baumannii cells undergo a maximum of a 22% dilution in the intracellular antibiotic concentration. Antibiotic dilution mediated by changes in S/V could provide a significant fitness advantage for antibiotics with steep growth inhibition curves  Similar to panel A but with a kon of 1 μM−1 h−1 and a koff of 10 h−1. For the full set of parameters, see k and Pin, setting Pout as 0.1 μm h−1, (S/V)min as 3 μm−1, and (S/V)max as 15 μm−1. (D) Maximum possible antibiotic dilution (δmax) versus Pout. Here, the growth rate is kept fixed (k = 1 h−1). The maximum possible antibiotic dilution decreases with increasing Pout and has the highest value for Pout of 0 μm h−1  Antibiotic dynamics for different 0 μm h−1 . DownloaCopyright © 2022 Ojkic et al.2022Ojkic et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the E. coli cells are treated with membrane-targeting and membrane transport-targeting antibiotics, the cell surface area and volume decreased  that can bind to the membrane per unit surface area and per unit time with a probability Pon. Therefore, an increase in S/V decreases the density of membrane-bound antibiotics, thereby providing a beneficial morphological adaptation for countering the action of the antibiotic.In contrast to cytosolic antibiotics, when ecreased , whereasecreased . The decThe mechanisms by which antibiotics induce cell shape changes are specific to the type of antibiotic treatment . DNA-tarE. coli cells are exposed to nutrient or CHL perturbations, the bacterial cell aspect ratio remains constant at ~4 , which inhibits bacterial translation. When actively translating ribosomes are blocked by CHL, cells synthesize new ribosomes in excess to counterbalance their inactivation . This innt at ~4 , implyin 2πV−1/3 . Therefodecrease  and B.S/V increases or decreases upon chloramphenicol treatment depending on nutrient availability in the growth environment 1/3 (k) or division protein synthesis (Fk) depending on nutrient availability. In nutrient-rich medium, cells allocate more ribosomes to division than growth (k/Fk decreases), resulting in smaller cells and higher S/V. The increase in S/V provides an adaptive benefit by importing more nutrients to counter growth inhibition by the antibiotic. In contrast, in nutrient-poor medium, cells tend to allocate more ribosomes to growth than division (k/Fk increases), resulting in larger cells and smaller S/V. A reduction in S/V reduces antibiotic influx, which is more beneficial for survival if nutrient availability is low.Experimental data, however, show that ironment  1/3 . Upon trkF/k)1/3 . The excE. coli cells, our model can quantitatively capture the experimentally observed trends for the dependence of S/V on the antibiotic concentration in different nutrient environments  typical for aminoglycosides: hygromycin B (Ak = 5 μM−1), chloramphenicol (Ak = 5.8 μM−1), streptomycin (Ak = 10 μM−1), and paromomycin (Ak = 19 μM−1). Depending on the ratio of the membrane permeability constants (Pin/Pout), the antibiotic dilution factor is nonmonotonic and reaches a maximum for a Pin/Pout value of ~1 , Pin/Pout is ~0.18, and for bacteria lacking efflux pumps (ΔtolC), Pin/Pout is ~0.66 , the cell becomes more curved, and the cell width increases . Similarly, when E. coli cells are exposed to DNA-targeting antibiotics that are also translocated inside the cell by OmpF, the expression level of ompF decreases within 30 to 120 min after antibiotic treatment , 5049, 5pression , creatinpression , resultiux pumps , 54 (Figux pumps . In the


Clostridioides difficile infection, continue to serve as significant threats in the United States, with increasing incidence in the community setting. While much attention has been granted towards antimicrobial stewardship in acute care settings, the transition to the outpatient setting represents a significant yet overlooked area to target optimized antimicrobial utilization. In this article, we highlight notable areas for improved practices and present an interventional approach to stewardship tactics with a framework of disease, drug, dose, and duration. In doing so, we review current evidence regarding stewardship strategies at transitional settings, including diagnostic guidance, technological clinical support, and behavioral and educational approaches for both providers and patients.Inappropriate antibiotic use and associated consequences, including pathogen resistance and  Clostridioides difficile infection (CDI), associated with antimicrobial use, the toll in the United States rises to over 3 million infections and 48,000 deaths [Since the initial advent of penicillin in 1928, mankind has been enveloped in a persistent race against the inevitable rise of antibacterial resistance. With antibiotic-resistant infections estimated to affect approximately 2.8 million Americans and causing mortality in 35,000 cases annually, the relevance of this threat has only increased over time [Escherichia coli (ESBL-EC) and Klebsiella pneumoniae (ESBL-KP) within the Southeastern United States between 2009 and 2014, the incidence of ESBL-EC infections increased significantly from 11.1 infections/100,000 patient days in 2009 to nearly double by 2014 at 22.1 infections/100,000 patient days. This increase was largely driven by rises in community-associated and healthcare-associated ESBL-EC infections, with relatively subtle uptrends in hospital-acquired infection [Escherichia coli have also been seen, increasing from 17.2% in 2003 to 22.2% in 2012 [Escherichia coli and Klebsiella pneumoniae, which increased significantly in Europe from 0.1% and 8.4% of isolates, respectively, in 2016 to 0.2% and 10% in 2020 [According to an epidemiologic evaluation of extended-spectrum beta-lactamase (ESBL)-producing nfection . Similar in 2020 .Enterococcus faecium from 11.6% in 2016 to 16.8% in 2020 was observed [Gram-positive resistance, while not escalating to the same degree as its Gram-negative counterpart, also remains concerning. Despite national targeted activity to decrease the incidence of MRSA infection, longitudinal surveillance data in the United States suggest that the rate of decline has started to slow in more recent years. Between 2005 and 2012, hospital-onset MRSA bloodstream infections demonstrated an annual decline of 17.1%, but then plateaued and did not significantly change from 2013 to 2016. In contrast, community-onset MRSA infections showed an overall less profound reduction, dipping by 6.9% per year from 2005 to 2016 [Nearly 80–90% of human antibiotic use occurs in the outpatient setting, according to public health data gathered from the United Kingdom and Sweden, an estimate that has been presumptively adopted by other countries such as the United States . SimilarWhile most outpatient prescriptions are initiated directly in the community, antibiotic prescribing at transitions of care (TOC) serves as a considerable, though relatively neglected, area when evaluating the totality of outpatient antimicrobial utilization. Approximately half of hospitalized patients are prescribed antibiotics during their inpatient stay, with more than one in eight continued at discharge . PatientGiven the continued growing impact of antimicrobial resistance and other ancillary consequences associated with inappropriate antimicrobial use, it is clear that there is a meaningful need for antimicrobial stewardship in the community setting but also at transitions of care. In this review, we summarize current evidence for transitions of care and outpatient stewardship initiatives, outline elements driving suboptimal antimicrobial use, and present interventional strategies for healthcare professionals seeking to strengthen stewardship practices.In 2014, the CDC first introduced the Core Elements of Hospital Antibiotic Stewardship Programs as part of a national call to action in addressing the growing threat of antimicrobial resistance . AcknowlNumerous studies have sought to investigate the impact of various stewardship strategies in order to provide insight for developing practice frameworks and demonstrate support for dedicating resources toward stewardship activities. A 2005 systematic review of 39 studies conducted in primary care and ambulatory clinics examined a variety of activities, including printed educational materials, audit and feedback, educational meetings and outreach visits, financial and system-based changes, patient-based interventions, and multi-faceted interventions, and found that of these actions, a multi-faceted approach involving educational interventions on many levels, targeting healthcare providers, patients, and the general public, had the most magnitude in effect size . These fSparked by the identification of opportunities for improved prescribing in this setting, applications of similar strategies during transitions of care have arisen more recently. In a 2019 systematic review of 40 paired hospital and nursing home sites, Dickinson and colleagues reported that approximately 30% of transitions involved an inappropriate change to the antibiotic plan of care, thus establishing a significant area ripe for improvement . With inStrategies of prospective audit and feedback coupled with education have demonstrated success in improving appropriate antibiotic prescribing and shown benefits towards other ancillary outcomes, such as a reduction in antibiotic days of therapy and hospital readmission rates . In a prAt the core of all prescribed therapeutic antibiotic regimens is a targeted disease; thus, the foundation of a suitable antibiotic prescription is first reliant on appropriate diagnosis and triaging a need for antibiotics. Overdiagnosis contributing to inappropriate antibiotic use can occur when a clinical diagnosis is made without fulfilment of diagnostic criteria, or when a diagnosis is made for a disease that would not have caused any symptoms or harm, thus rendering treatment to be superfluous ,28. One 4 CFU/mL to > 105 CFU/mL for the processing of potential uropathogens was accompanied by lab report commentary stating that organisms present in quantities between 104 and 105 CFU/mL were usually representative of ASB and advising clinicians to call for workup if there was high clinical suspicion for UTI. This intervention led to a decrease in prescribing ASB for patients with colony counts within this range from 38% prior to the intervention to 10% after, with no significant changes in clinical outcomes. Less than 10% of samples were requested for workup on the basis of clinical suspicion, although, when workup was requested, it was found that these patients were more likely to have a UTI (35% vs. 7%), suggesting more thoughtful provider discernment of the clinical indicators of infection [Another systemic strategy for ASB stewardship in the diagnostic process includes partnering with the microbiology laboratory to decrease unnecessary screening and the overinterpretation of laboratory results . Diagnosve a UTI % vs. 7%,Accurate diagnosis is a critical first step in determining appropriate therapeutic management, with the second being adequate triaging for antibiotic need. Overprescribing occurs when antibiotics are given for conditions in which they are not indicated, such as in the common scenario of acute upper respiratory tract infections. With many acute respiratory tract infections being viral in origin, strategies aiming to dissuade antibiotic initiation may prevent the prescribing of these agents for indications in which they lack a benefit. Even a simple reminder, such as the display of a public commitment poster for judicious antibiotic use in patient examination rooms in a randomized controlled trial across five outpatient primary care clinics, was seen to help influence clinician decision-making and decrease inappropriate antibiotic prescribing for acute upper respiratory tract infections by approximately 20% . UtilizaEscherichia coli found that receiving at least one fluroquinolone prescription preceding the diagnosis of resistance was associated with a higher risk of fluoroquinolone-resistant E. coli colonization or infection, with the risk of resistance highest in the first year after the antibiotic is taken (OR 2.67) and progressively decreasing to undetectable after two years (OR 1.09) [Once an infectious disease warranting treatment is identified, selection of an appropriate drug is the natural next step in building an antibiotic regimen. In the setting of drug selection, stewardship opportunities arise in determining the need to select a drug at all, as well as the nuances of selecting an optimal, as compared to simply suitable, antibiotic agent. While multiple drugs may all adequately treat an indication, stewardship efforts to optimize medication selection based on evidence-directed practice may improve overall appropriate antibiotic use and minimize collateral consequences such as the development of resistance, the risk of which may persist beyond the immediate antibiotic course. One recent case–control study evaluating fluoroquinolone resistance in OR 1.09) . Thus, jOR 1.09) . AnotherOR 1.09) . CollectOR 1.09) . By inveOR 1.09) .Antimicrobial dosing inaccuracies pose considerable opportunities for improved prescribing practices, with issues arising both from general prescribing errors as well as failure to account for clinical changes occurring during a patient’s course. Previous studies seeking to characterize the incidence of prescribing errors estimate that approximately seven to eight percent of prescriptions contain errors, with antibiotics serving as the leading drug class with prescribing mistakes and reported to account for between 20% and 50% of all observed errors ,45. Furt2 to identify the individual’s latest eGFR, as well as general dose recommendations in the form of adjustment ratios for various eGFR ranges . This strategy only resulted in a mild and not statistically significant reduction in the rate of inappropriate prescriptions, with 20.4% of orders being inappropriate in the non-alert period as compared to 18.5% following alert implementation [Of the various elements involved in determining antibiotic dosing, evaluation of renal function remains one of the most robust areas in which substantial gaps exist in appropriate prescribing. With many antibiotics  eliminated via glomerular filtration, dosage adjustment will be required based on either the estimated glomerular filtration rate (eGFR) or creatinine clearance (CrCL). Patients with reduced renal function, whether acutely or chronically, are at the highest risk of antibiotic dosing errors. The majority of investigation into antibiotic dosing with renal impairment has been conducted in the setting of chronic kidney disease (CKD), with studies reporting alarming incidences of inappropriately high doses across various clinical locations. One study conducted by Farag and colleagues found that of 1464 antibiotic prescriptions written for ambulatory care patients with CKD, an average of 64 per 100 prescriptions were dosed in excess . Other sentation . Taken tentation .> 7 days or even CKD if > 90 days, though, in most instances, renal function will generally recover after the offending etiology has been addressed and supportive measures have been provided. Unlike in CKD, where routine overdosing is the most prevalent issue, AKI presents risks for antibiotic underdosing in the setting of dynamic fluctuations in renal clearance [While much attention has been given to the occurrence of antibiotic overdosing in the setting of chronic kidney disease, comparatively little has been afforded to the counterpart of acute kidney injury (AKI). By definition, AKI refers to an abrupt deterioration in renal function that may be precipitated by a multitude of factors, including infectious diseases. AKI is a fairly common complication observed in patients presenting for hospitalization, with estimates of approximately 15% occurrence in standard inpatients and reaching up to 60% prevalence amongst those who are critically ill . AKI maylearance ,55. In tlearance . Thus, lClostridioides difficile infection, in addition to the global risk for the emergence of resistance. Out of all of the four core determinants, the duration of therapy has repeatedly been identified as the leading area in which gaps exist between guideline-recommended therapy and prescribing practice, especially at transitions of care. In one study, discharge antibiotic prescriptions from a 300-bed teaching hospital were examined for appropriateness. Of the 236 prescriptions identified, only 21% were appropriate for the duration prescribed as compared with drug choice (74%), dose (64%), or frequency (64%); additionally, the vast majority (71%) of prescribed durations exceeded guideline-recommended lengths of treatment [The final component in crafting an appropriate antibiotic regimen after all other pre-requisite diagnostic, drug choice, and dosing factors are appropriately fulfilled is the determination of the duration of therapy. Duration of therapy serves as an important target for antibiotic stewardship, as unnecessarily prolonged courses increase the individual patient risk for adverse effects and reatment . These freatment . With moVarious interventions targeting the optimization of antibiotic duration have been evaluated, with strategies employing technological support such as CDSS and pre-populated order sets, as well as personal approaches of classic audit and feedback, being the most studied. Sophisticated CDSS and order sets designed with stewardship goals in mind can serve as highly effective global techniques in improving antibiotic prescribing, particularly with the incorporation of default durations or suggested stop dates. In a multicenter retrospective interventional study, a CDSS consisting of diagnosis-specific antibiotic prescription discharge order sets containing default dose and dispense quantities was implemented within 14 emergency departments. Following implementation of the CDSS, with an overall provider utilization of 60.4%, rates of guideline-concordant antibiotic prescribing increased significantly from 19.1% to 28.1%, with improved appropriateness of antibiotic duration (from 38.8% to 51.1%) serving as the driving factor. These changes were even more pronounced in the post-hoc analysis conducted to assess prescribing practices with versus without the use of the CDSS, which found an improvement in duration from 38.5% to 71.1% . AnotherIn conjunction with computerized strategies, prospective audit and feedback performed by stewardship teams have also demonstrated success in improving the appropriate antibiotic duration and have the benefit of personal engagement. Direct, verbal recommendations made by infectious diseases pharmacists to primary team prescribers regarding appropriate durations of therapy for 600 patients treated for CAP significantly lowered the median days of therapy from nine in the historical group to six in the post-intervention group, thereby circumventing a total of 586 days of unnecessary antibiotics over a six-month period. This audit and verbal feedback also increased guideline-concordant prescribing rates from 5.6% to 42% . ImportaAs utilized in many stewardship studies, multifaceted interventions including both a recommendation component coupled with education demonstrate a positive impact on optimizing immediate antibiotic use and also have the added benefit of engaging healthcare personnel directly and promoting overarching practice changes. Recent evaluations regarding prescriber perceptions of their antibiotic knowledge and practice suggest that not only are there opportunities for improved knowledge but also a general desire for more education. In one survey administered to house staff physicians at Johns Hopkins Hospital, 88% of respondents agreed that antibiotics are generally overused, with 72% acknowledging that overuse occurs within their own hospital. Results from the ten-question antimicrobial assessment written by an infectious diseases physician indicated that respondent knowledge of antibiotic use was generally low—the overall average score was 28%, with scorers achieving approximately 37% on the basic questions and 15% on the more advanced. The vast majority of respondents (90%) indicated that they wished for greater antimicrobial education and 22% stated that they had not received any formal antimicrobial education within the past year. These findings indicate that prescribers are generally aware of the issue of suboptimal antibiotic use, appear receptive to educational efforts, and may benefit from increased antimicrobial teaching . There aWhile educational sessions have often traditionally been conducted in a didactic lecture format, utilization of online modules and technological platforms has grown as an attractive option to promote interactive engagement and the application of teaching points. This technique originally surfaced in the earlier phases of medical education targeting student trainees, where web-based distance learning with modules focusing on antimicrobial use and microbial resistance significantly improved assessment performance and student-reported knowledge gain . When apEducation-based initiatives can be bolstered further when coupled with performance feedback; by collecting prescribing data following educational outreaches and transparently sharing these results with participants, prescribers may benefit from increased awareness of prescribing practices, evaluate comparative standing when benchmarked amongst peer use, and monitor individual progression over time. Such “behavioral interventions”, as these feedback approaches are commonly referred to, have demonstrated promise in optimizing antibiotic use. In one interventional study, 30 primary care providers (PCPs) attended a regularly scheduled regional meeting in which education on inappropriate antibiotic prescribing consisted of evidence-based guideline review for acute respiratory tract infections and the dissemination of a pocket-guide prescribing algorithm. Following this session, an unblinded email report outlining a peer comparison of inappropriate prescribing rates was emailed to each PCP on a biweekly basis. After one year of this education and feedback strategy, inappropriate antibiotic usage for respiratory tract infections decreased from 51.9% to 31.0%, and further fell to 16.3% following an additional year of continued open feedback . AnotherWhile prescribers undoubtedly serve as a major target to focus antimicrobial stewardship education, patients also serve as an important population to empower with greater antibiotic understanding. In a world of increasing evidence-based practice and broadening healthcare advancements, historical paternalistic models of medicine have largely been replaced with practices that emphasize shared decision-making and patient-centered care. Not only are patients an important influence in the prescribing process, in many areas of the world where antibiotics are available without prescription, patients may also independently engage in self-medication with antibiotics (SMA), often inappropriately. The prevalence of SMA varies between countries, with ranges reported between 19% and 82% in Middle Eastern countries and 7.3% and 85.59% in Southeast Asian regions ,72. PropThe value of including patients in stewardship efforts has been demonstrated in several published works. In a randomized controlled trial focusing on acute bronchitis in general practice settings, patients provided with an educational leaflet describing the natural course of lower respiratory tract infections and advantages and disadvantages of antibiotic use demonstrated less antibiotic use (47%) as compared with patients who did not receive the leaflet (62%) . SimilarOverall, there exists an abundance of possibilities for stewardship expansion into the transitions of care setting, with a variety of opportunities across all four facets of antibiotic determinants of therapy. However, in addition to identifying such areas of opportunity and interventional measures to address them, the steward must also be armed with an understanding of the factors that may initially pose barriers in the pursuit of their initiatives. A systematic review of 35 studies seeking to understand intrinsic and extrinsic factors driving physician antibiotic behavior found that complacency in prescribing antibiotics to fulfill perceived patient expectations and fear of complications or patient loss were the most dominant physician attitudes reported, and sociodemographic factors such as university education also influenced clinical practice . As discIncreasingly, antibiotic prescribing at transitions of care is growing as an important sector in the ongoing battle against antimicrobial resistance. For the emerging steward, the established literature and CDC guidance support targeting efforts on the most high-yield disease states for which antibiotics may be inappropriately prescribed, including acute respiratory tract infections, urinary tract infections, and skin and soft tissue infections. Across the board, strategies involving the integration of clinical decision support tools with the implementation of audit and feedback coupled with peer comparison and accountability can help stewards in the transitions of care setting to optimize antibiotic prescribing with attention to disease, drug, dose, and duration. Further progression of stewardship activities in this realm should ideally emphasize patient engagement and education, as the patient remains the singular constant across the continuity of care and may serve as a powerful advocate in their medical management and an influencer of antibiotic use. Additionally, collaboration with other stakeholders, such as electronic health record vendors, insurers, and local health departments, may enhance stewardship efforts through improved monitoring and the potential to more accurately measure antibiotic use in this dynamic setting. Finally, stewards working in the transitions of care setting are uniquely poised to partner with both inpatient and outpatient care teams, where increased communication between these settings of care may reduce the potentiation of errors, provide a more comprehensive view of a patient’s care, and optimize overall medical management.


Escherichia/Shigella and Bifidobacterium increased  but that of Bacteroides decreased (p = 0.02) in the antibiotic treatment group. The microbiome of the antibiotic treatment group exhibited an alpha diversity lower than that of the control group. Thus, systemic antibiotic administration in early infancy affects the gut microbiome composition even after a month has passed; long-term studies are needed to further evaluate this.Long-term antibiotic use can have consequences on systemic diseases, such as obesity, allergy, and depression, implicating the causal role of gut microbiome imbalance. However, the evaluation of the effect of antibiotics in early infancy on alterations to the gut microbiome remains poorly understood. This study aimed to evaluate the gut microbiome state in infancy following systemic antibiotic treatment. Twenty infants under 3 months of age who had received antibiotics for at least 3 days were enrolled, and their fecal samples were collected 4 weeks after antibiotic administration finished. Thirty-four age-matched healthy controls without prior exposure to antibiotics were also assessed. The relative bacterial abundance in feces was obtained via sequencing of 16 S rRNA genes, and alpha and beta diversities were evaluated. At the genus level, the relative abundance of  The collection of microorganisms, including bacteria, archaea, and eukarya, that colonize the gastrointestinal tract is called the “gut microbiota” . During Antibiotics are designed to target and inhibit microorganisms  and are Baseline characteristics, including sex, growth, and delivery mode, did not vary significantly between the antibiotic-treated and control groups , and botFirmicutes and Bacteroidetes phyla in feces from the antibiotic treatment group were lower than those of the control group (average relative abundance-antibiotic treatment group (ARA-A) 24.6% vs. average relative abundance-control group (ARA-C) 35.3%, p = 0.015, and ARA-A 3.1% vs. ARA-C 7.0%, p = 0.049, respectively), while the abundance of Actinobacteria was significantly increased to that of the control group   .Escherichia/Shigella and Bifidobacterium increased  in the antibiotic treatment group compared with those of the control, while the abundance of Bacteroides decreased   .Firmicutes genera, such as Allobaculum, Enterococcus, and Candidatus Arthromitus, for which their abundances were threefold higher than those in the control group. The abundances of the Proteobacteria genera Klebsiella and Actinobacteria genera Bifidobacterium were fourfold and at least threefold higher, respectively, than those in the control group  effect size  to investigate the differences in taxa between groups using the Quantitative Insights Into Microbial Ecology (QIIME) pipeline. The antibiotic treatment group contained ol group .p = 0.033, p = 0.029, and p = 0.009, respectively) between the control and antibiotic treatment groups.Taxonomic analyses suggested that the microbiome of the antibiotic treatment group exhibited an alpha diversity lower than that of the control group . Chao1, p = 0.018), but it was not evident in the unweighted UniFrac analysis (p = 0.247).A three-dimensional principal coordinates analysis (3D PCoA) was performed to visualize the microbial community’s structure based on weighted and unweighted UniFrac distances. A significant change in the microbial community structure with antibiotic treatment was shown in the weighted UniFrac analysis (The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis performed demonstrated a significant difference in gut microbiome metabolic activity between the two groups . SignifiOur study shows that antibiotic administration to infants younger than three months old can impact their gut microbiome. We used 16S ribosomal RNA (16S rRNA) amplicon sequencing to analyze the bacterial community composition found in stool samples obtained from 34 healthy infants and 20 antibiotic-treated infants at least 4 weeks after the end of antibiotic treatment. The gut microbiome differed in composition between both groups, and the lower alpha diversity in the antibiotic treatment group indicated lower microbiome richness and evenness. Moreover, the influence of antibiotics early in life relative to gut microbiota remained even after a few weeks.Antimicrobial agents are among the most frequently used pharmaceuticals in infants and children. Cox and Blaser recently estimated that by 2 years of age, children in the United States have, on average, received nearly three courses of antibiotics and that this will increase to approximately 10 courses by the age of 10 years . These fProteobacteria and decreased abundance of Bifidobacterium confirmed that antibiotic exposure at the beginning of life greatly influenced the diversity and composition of infant microbiota. In addition, the microbiota of untreated infants, but whose mothers received antibiotics prior to delivery, showed the same changes observed in the microbiota of treated infants [Bifidobacterium and Bacteroides within their gut microbiome [Bacteroides decreased, corresponding to that observed with babies born by C-section [Bifidobacterium [Lactobacilli and Bifidobacteria and enhance that of mastitis-inducing bacteria in breast milk, causing decreased bacterial diversity [Previous studies have monitored the intestinal microbiota of infants who underwent antibiotic treatment in the first few days of life and have traced the effects up to 4 and 8 weeks after birth ,32. A si infants . Interescrobiome ; however-section . Similaracterium , but antiversity . This diiversity .Bacteroidetes division and a higher number of members of the Firmicutes division. In this study, the bacterial taxa composition of the antibiotics treatment group showed threefold higher abundances of Firmicutes than those of the control group  and T helper (Th) subset balance. The pathophysiology of allergic and autoimmune disease is thought to be driven by the excessive activation of either Th1 or Th2 cells. Additionally, recent studies revealed that Th17 cells and Tregs play a key role in immune homeostasis . The balol group .However, there are conflicting opinions regarding the effects of antibiotic routes of administration on gut microbiota . One stuA limitation of this study is that serial the consequences of antibiotics early in life were not documented because of the retrospective nature of the study. The participants were treated with two antibiotics, and the effect of each antibiotic alone was not described. Moreover, all data were represented by relative abundances; no absolute quantification was performed. Therefore, a long-term follow-up evaluation for the participants of our study is needed, and further investigation of the mechanisms of immunology and metabolites should be completed to enable a greater understanding of the gut microbiome.With the increase in research in microbial communities and the greater availability of “multiomic” techniques , many stTwenty infants under 3 months of age who received systemic antibiotic treatments were included in the antibiotic treatment group. They were hospitalized for fever and were treated intravenously with ampicillin/sulbactam 150 mg (as ampicillin dose) per kg per day and cefotaxime 150 mg per kg per day for at least 3 days. All infants in the antibiotic treatment group were born (1) between 37- and 42-weeks gestation; (2) with a birth weight between 2.5 and 4.5 kg; and (3) without any adverse event. Thirty-four age-matched healthy controls who had not been exposed to antibiotics were selected. Stool samples were obtained in both groups. Feces from the antibiotic treatment group were sampled at least 4 weeks following the cessation of antibiotic treatment. We excluded infants who were born (1) from mothers who had group B streptococcus infection and chronic diseases, such as diabetes, hypertensive disorders, or autoimmune disease; (2) from mothers who had taken oral antibiotics during the third trimester of pregnancy; and (3) those born vaginally 12 h after amniotic sac breakage. This study was approved by the Institutional Review Board (IRB) of Ethics Committee of Cha Bundang Medical Center (IRB no. 2017-02-31), and written informed consent was obtained from the parents.Fecal samples from newborns were collected from diapers using sterile swabs and were immediately transferred to sterile cryogenic tubes and stored at −20 °C until delivery to the laboratory. Samples were then stored at −80 °C until DNA extraction.The total genomic DNA was extracted from 200 mg of stool sample using a QIAamp Fast DNA Stool Mini Kit  with additional bead beating following the manufacturer’s instructions. DNA concentration was measured using a UV-visible spectrophotometer (Nanodrop 2000 c (Thermo Fisher), Waltham, MA, USA). DNA samples were stored at −20 °C for subsequent experimentation.® ONE dsDNA System . The products’ size and quality were evaluated on a Bioanalyzer 2100 . The pooled libraries were sequenced using an Illumina MiSeq instrument with a MiSeq v3 Reagent Kit .The composition of newborn microbiota was analyzed using 16S rRNA amplicon sequencing with Illumina MiSeq . For sequencing, the V3-V4 regions of the bacterial 16S rRNA gene were amplified using primer set F319 (5′-TCGTCGGCAGCGTCAGATGTGTATAAGAGACAGCCTACGGGNGGCWGCAG-3′) and R806 (5′-GTCTCGTGGGCTCGGAGATGTGTATAAGAGACAGGACTACHVGGG TATCTAATCC-3′). DNA templates (12.5 ng/µL) were amplified using a KAPA HiFi Hotstart PCR Kit  with 5 µM of primers. Reaction conditions were as follows: 95 °C for 3 min; 25 cycles of 95 °C for 30 s; 55 °C for 30 s; and 72 °C for 30 s, with a final extension at 72 °C for 5 min. After PCR cleanup, a secondary amplification to attach Illumina Nextera barcodes was performed using i5 forward and i7 reverse primers. The DNA was amplified according to the manufacturer’s protocol. The PCR products were purified using an Agencourt AMpure XP PCR Purification Kit . The purified products were quantified using a QuantiFluort-test) or non-parametric tests (Mann–Whitney U test); a p value was assessed as significant when <0.05.An analysis of the 16S rRNA gene sequences was performed using the QIIME (v.1.9.1) bioinformatics pipeline . Using qualified sequences , the OTUs were identified based on an open-reference picking method using 97% identity to entries in the Greengenes database (v13_8)  using UCLUST . A sample alpha diversity was calculated using the phylogenetic distance and the number of observed OTUs. For beta diversity comparison between groups, weighted/unweighted UniFrac distances were evaluated . Statistical comparisons of groups were performed with the non-parametric multivariate analysis of variance methods using the Adonis function in the vegan R package. PICRUSt, which is a bioinformatics software package designed to predict metagenome functional content from marker gene  surveys and full genomes, was performed for the analysis of differences in gut microbiome metabolic activity between the two groups. The linear discriminant analysis effect size (LefSE) was determined using the LDA log score (cut-off ≥ 3) to identify distinct taxonomic bacterial biomarkers. The comparisons between groups were analyzed using parametric (Student’s https://www.ncbi.nlm.nih.gov/bioproject/PRJNA802976 (accessed on 4 February 2022)) and Sequence Read Archive (SRA) accession numbers: SRR17868041–SRR17868094.Raw data files in fastq.gz format were deposited into National Center for Biotechnology Information (NCBI) database and are available at BioProject under accession number PRJNA802976 (Here, we demonstrated that exposure to systemic antibiotics in early infancy can change the composition of the gut microbiome even after a single month.Antibiotics are fundamentally important, and their use has played a pivotal role in improving human health However, we propose that clinicians consider the administration of antibiotics during early infancy more carefully and try to minimize long-term risk with adjunct treatments by understanding the effects of antibiotic-induced disorders. A long-term follow-up in large samples is needed to study the systemic or metabolic effects of antibiotics.


Inappropriate use of antibiotics is among the key drivers of antimicrobial resistance (AMR). Antibiotic use in Northern Ireland (NI) is the highest in the UK and approximately 80% is prescribed in primary care. Little information however exists about the patient and prescriber factors driving this. We described the trend in NI primary care total antibiotic prescribing 2010–2019 and conducted a cross-sectional study using a random sample of individuals registered with an NI GP on 1st January 2019. We used multilevel logistic regression to examine how sociodemographic factors and urinary catheter use was associated with the likelihood of being prescribed an antibiotic during 2019, adjusting for clustering at GP practice and GP federation levels. Finite mixture modelling (FMM) was conducted to determine the association between the aforementioned risk factors and quantity of antibiotic prescribed (defined daily doses). The association between age and antibiotic prescription differed by gender. Compared to males 41–50 years, adjusted odds of prescription were higher for males aged 0–10, 11–20 and 51 + years, and females of any age. Catheter use was strongly associated with antibiotic prescription . Socioeconomic deprivation and urban/rural settlement were not associated in the multilevel logistic analysis. GP practices and federations accounted for 1.24% and 0.12% of the variation in antibiotic prescribing respectively. FMM showed associations between larger quantities of antibiotics and being older, male and having a catheter. This work described the profile of individuals most likely to receive an antibiotic prescription in NI primary care and identified GP practice as a source of variation; suggesting an opportunity for reduction from effective interventions targeted at both individuals and general practices. Antimicrobial resistance (AMR) describes the process by which an organism develops resistance to an antibiotic with the result it can no longer be used to treat an infection. In 2016, the O'Neill review [In response to the O'Neill review, the UK government set out an ambition to halve inappropriate antibiotic consumption in the UK by 2020, and the Department of Health, Northern Ireland endorsed this target for NI. The factors influencing antibiotic consumption, however, are complex  and the The association between antibiotic consumption and age is well-described in both the UK and Europe with people in the youngest  and oldeIn addition to socio-demographic factors, we know that antibiotics are used to treat infections and we know the risk of infection can increase in the presence of co-morbidities. One such factor is the use of a urinary catheter. According to the National Institute for Health and Care Excellence (NICE), catheter-associated urinary tract infections (CAUTIs) comprise a large proportion of healthcare-associated infections (HCAIs)  and nearAs well as individual factors, the clinical responsibility to prescribe antibiotics lies with a person's General Practitioner (GP). We know the decision to prescribe an antibiotic is influenced by several factors including the ability to make diagnostic decisions, particularly with older patients and those in vulnerable groups, managing patient expectations and having knowledge of alternatives, such as delayed prescriptions . This caThe study objectives are to; (1) describe trends in primary care antibiotic prescribing for all antibiotics, to establish a baseline against which the impact of interventions can be assessed and; (2) understand the epidemiology of antibiotic prescribing in primary care, with a view to potentially identifying groups who could benefit from targeted interventions to reduce antibiotic consumption in primary care.Two extracts of the NI Enhanced Prescribing Database (EPD) were received from the NI regional data warehouse. The EPD is a regional system containing information about all prescriptions dispensed by community pharmacies in NI and is described in greater detail in other work .www.nisra.gov.uk) were added to the aggregated dataset to enable calculation of annual prescribing rates.The first extract was an aggregated dataset containing the annual quantity of antimicrobials/antibiotics  prescribed to each individual in NI in defined daily doses (DDDs) for all NI GP practices from 2010 to 2019. Northern Ireland Statistics and Research Agency (NISRA) mid-year population estimates . HCN was available for 100% of patients in the GP register and approximately 85–90% of prescriptions in the EPD.The annual antibiotic prescribing rate for NI  between 2010 and 2019 was calculated from the aggregated dataset using the formula:  × 1000.Total individual prescribed DDDs were collapsed into a binary variable. Individuals with DDDs greater than zero were categorised as ‘Yes’, individuals with DDDs equal to zero were categorised as ‘No’.total number of DDDs) was the outcome for the sub-analysis.A sub-analysis was then conducted on a subset of the main dataset containing only individuals who had been prescribed an antibiotic in 2019. The individual total prescribed antibiotics during 2019 (www.nisra.gov.uk), settlement band  based on individual's postcode (www.nisra.gov.uk) and catheter use (Yes/No) during 2019.Sociodemographic and health-related risk factors used  included; individual's age at the start of the study period, sex, Northern Ireland Multiple Deprivation Measure 2017 (NIMDM 2017) quintile based on individual's postcode .Given that sufficiently large samples will almost always demonstrate significant differences when using a statistical test – unless no effect whatsoever exists  – a simpThe aggregated dataset was used to plot the NI annual prescribing rate  over time.The individual-level analysis was carried out in two distinct phases; 1. Multilevel logistic regression analysis  to identify factors associated with the prescription (Yes/No) of any antibiotic; 2. Multilevel linear regression analysis (with the same random effects) to identify factors associated with the quantity of antibiotic prescribed (measured in DDDs).Univariable multilevel logistic regression analysis was conducted to ascertain the association between the log-odds of receiving an antibiotic (DDDs greater than zero) and each of the risk factors. The assumption of linearity between age and antibiotic prescription was assessed by comparing models including age, and in turn, square, cubed and quartic functions of age, employing the likelihood ratio test (LR test) to compare model fit at each stage. Where non-linearity was indicated, age-groups were derived and used in place of continuous age in both univariable and multivariable analyses. Ten-year age-groups were chosen to minimise the loss of information due to categorisation.The assumption of independence was assessed in each univariable model by including both GP practice and federation as random effects and using the approximate likelihood ratio test to compare the mixed-effects against fixed effects models to assess if the variance components for each of the random effects were significantly different from zero. Due to the multitude of evidence suggesting a difference in antibiotic prescribing to males and females, consideration in both univariable and multivariable analyses was given to interactions between sex and all other covariates; sex and deprivation, sex and settlement band, sex and catheter use, and sex and age group. All risk factors and interactions that had been significant (at the 0.05 level) in the univariable analysis were entered into a multivariable logistic regression analysis in a forward-stepwise fashion. Sex and age group were retained in all multivariable models regardless. Confounding was considered at each step of the model-building process, defined as a change of more than 10% in the odds ratio (OR) of parameters still in the model with the addition or removal of the confounder. Interactions were considered during multivariable analysis with main effects entered initially, then removed and replaced by the interaction term. The LR test and Akaike information criterion (AIC) were used to compare fit.Secondly, a sub-analysis was conducted focusing only on individuals who received an antibiotic during the year 2019 (DDDs greater than zero). Univariable and multivariable analyses were conducted using the same approach described above with total number of DDDs prescribed during 2019 as the outcome variable. Confounding was defined as a change of more than 10% in the regression coefficient of parameters still in the model with the addition or removal of the confounder. Post-regression analysis using residual-versus-fitted and quantile-quantile plots suggested deviation from normality, non-constant variance and a trend in residuals. To overcome this, a log-transformation  was performed on the outcome variable and the linear analysis repeated using the log-transformed outcome. Again, the residuals from the final model violated the assumption of normality, albeit not so strongly. It was also noted that the fit of the linear regression model was generally poor.a priori and models were estimated with seven, down to two classes. Convergence was achieved for the five and two class models and they were compared for fit against the final model from the simple linear regression analysis using the AIC. To further improve fit, risk factor variables that determined membership of each class were modelled, each entered into the model in a forward stepwise procedure and the AIC used to compare. The model with deprivation included did not converge. Once the final model had been estimated, the assumption of clustering was tested using the AIC to compare models with and without the cluster variables.To improve model fit and adherence to model assumptions, a finite mixture modelling (FMM) approach  was condAnalysis of the annual NI antibiotic prescribing rate was conducted using R version 4.1.0 for Windows , all othEthical approval was not necessary. No personally identifiable information was processed during this study, all data were anonymised prior to receipt.Between 2010 and 2019 the average prescribing rate was 9258.66 DDDs per 1000 inhabitants, ranging from 8467.84 DDDs per 1000 inhabitants in 2011 to 9735.43 DDDs per 1000 inhabitants in 2016. A clear downward trend was observed since 2016, when the O'Neill review was released .Fig. 1.n = 5729)  = 19–57). Fifty-four per cent of the sample was male and 99.3% of individuals had not received a catheter during 2019. There was a fairly even split across deprivation quintiles. The majority of individuals in the sample lived in an intermediate settlement band  .Table 1n = 3020) were prescribed an antibiotic during 2019.P < 0.001). Compared to people aged 41–50 years (the reference group) the odds of being prescribed an antibiotic were higher among those in the youngest age group (0–10 years) but similar among those aged between 11 and 40 years. The odds of being prescribed an antibiotic then increased exponentially from the age of 51 onwards.Females displayed almost double the odds of being prescribed an antibiotic compared to males . Compared to those living in an urban environment, odds of being prescribed an antibiotic were higher for those living in an intermediate area, but no difference was observed among those living in a rural area. People who used a catheter at least once during the study period displayed more than ten times the odds of being prescribed an antibiotic than those without a catheter .Deprivation was not significantly associated with being prescribed an antibiotic in the univariable analysis, with little difference in the odds observed across deprivation quintiles. Settlement band was almost significantly associated at the 0.05 level  and was better than the fixed effects logistic model (LR test P < 0.01).P < 0.001) in the final model. With the exception of males aged 21–30 and 31–40 years, the adjusted odds of being prescribed an antibiotic remained higher among males in all other age groups. Compared to males aged 41–50 years, the adjusted odds of being prescribed an antibiotic remained higher for females in all age groups. Settlement band was not significantly associated with antibiotic prescribing in the multivariable analysis but was retained as it improved the AIC of the final model. Having a catheter remained significantly associated with being prescribed an antibiotic (P < 0.001). Those who used a catheter at least once during the study period displayed almost seven times the odds of being prescribed an antibiotic than those who did not . The final model also included both random effects. Of the total variation in the odds of antibiotic prescribing, 1.24% was attributable to the variation between GP practices (intraclass correlation coefficient (ICC) = 0.0124) and 0.12% to the variation between GP federations (ICC = 0.0012).The interaction between age and sex was significantly associated with being prescribed an antibiotic (n = 3020) are shown in n = 1770).The results of the sub-analysis of the quantity of antibiotics measured in log-transformed DDDs prescribed to those who received an antibiotic during 2019 (P < 0.001). Compared to people aged 41–50 years; a smaller quantity of antibiotics was prescribed to people in the younger age groups. Number of log DDDs prescribed to those aged 51–60 years was similar to those aged 41–50 while an increase was observed among those who were older, with the exception of those aged more than 90 years. There was no association between sex and number of log DDDs prescribed (P = 0.137). Deprivation (P = 0.567) and settlement band (P = 0.236) were also not significantly associated in the univariable analysis.P < 0.001). None of the interactions investigated  were found to be significant in the univariable analysis and the variation in log DDDs did not differ between GP practices or federations, thus the univariable models were simplified to contain only fixed effects.Those who had used a catheter at least once during the year were prescribed significantly more than those without a catheter  and those aged 31–40 years had significantly lower odds (of being in the high antibiotic use/DDD class) than those aged 41–50 years . Comparison of clustered and non-clustered models indicated that assuming clustering did not improve model fit and so the simple fixed-effects model was chosen.P < 0.001). In the low antibiotic use/DDD class, a significant decrease in log DDDs was observed (compared to those aged 41–50 years) for those aged 0–10 years ) and 81–90 years ), while a significant increase was observed among those aged 61–70 years ). In the high antibiotic use/DDD class, compared to those aged 41–50 years, a significant decrease was again observed among those aged 0–10 years ) with an increase observed in the 71–80 age group ).Fixed-effect risk factors for each class included in the final model were: age group, sex, deprivation, settlement band and catheter use. Age was significantly associated with log DDDs (LR test P < 0.001). Females in the high antibiotic use/DDD class were associated with a decrease in log DDDs compared to males ). Deprivation was not significantly associated with log DDDs in either the high or low antibiotic use/DDD class but was retained in the final model as it confounded the relationship between settlement band and log DDDs. Settlement band was also not significantly associated with log-DDDs but was retained in the final model as it improved the model AIC. Catheter use was significantly associated with log-DDDs for individuals in both the low  and high antibiotic use/DDD classes . In the low antibiotic use/DDD class, those who had used a catheter at least once during 2019 were associated with an increase in log DDDs compared with those who had no catheter ). A similar trend was observed for individuals in the high antibiotic use/DDD class ).There was no significant association between sex and log DDDs in the low antibiotic use/DDD class but a significant association was observed in the high antibiotic use/DDD class . As in previous studies , 30, femOther possible explanations for this gender gap however include a mixture of psychological and socio-demographic factors, and some features of the health system itself . CognitiHaving had a catheter at some stage during the year was strongly associated with both antibiotic prescription and the amount of antibiotic prescribed. Due to the low prevalence of catheter use in the population, there was uncertainty around the estimates of antibiotic consumption in both analyses, reflected in the width of the confidence intervals. Having a catheter in-situ greatly increases the likelihood of a urinary tract infection (UTI) requiring antibiotic treatment  and may ‘unmet need’ has been similarly observed in at least one other NI-based study looking at prescribing of obesity medication [Interestingly, no association between deprivation and antibiotic prescription or quantity of antibiotics prescribed was found in either analysis. The link between socioeconomic deprivation and antibiotic prescribing has been well established and reported in several previous studies , 38 althdication . Finallydication  and moredication  leading No association was found between settlement band and either of the prescribing outcomes, although its inclusion in the models did improve model fit. Research around urban/rural settlement and antibiotic prescribing has so far produced ambiguous results with evidence supporting associations in both directions , 47. GivThe use of multi-level analysis enabled the ability to account for the role of GP practices and federations in antibiotic prescribing by adjusting for the hierarchical nature of the data. This adjustment may in itself account for some of the unusual findings including the lack of associations with deprivation and settlement band. Echoing previous work in England  and WaleThis analysis used a national primary care prescribing dataset to look at antibiotic use and associated sociodemographic risk factors. While clinical information wasn't directly available, catheter use was considered as a proxy measure. Catheter use is a known risk factor for infection  and so iThere were also a number of limitations. The cross-sectional study design limits the ability to directly observe causal relationships and makes it difficult to generalise the findings to time-periods beyond the scope of the study. This may be particularly important in the wake of the COVID-19 pandemic. Limited information about GP practices and their catchment populations also made it challenging to fully explain the observed between-practice and between-federation variation, while a lack of clinical information made it impossible to measure appropriateness of antibiotic prescribing.Using a national-level prescribing dataset it was possible to control for known confounders such as age and sex. Data were also available for catheter use, which is a known risk factor for urinary tract infections. However, in the general population the majority of antibiotics are given for respiratory tract infections and using the prescribing dataset it was not possible to measure other patient comorbidities that might increase the risk of infection, and therefore the need for antibiotics. Therefore, residual confounding due to unmeasured covariates is likely.It is also important to note the generally poor fit of the mixture models in the analysis of log DDDs. This is again likely explained by the absence of important covariates. While the mixture models showed improved fit over the simple linear regression model, they still accounted for only a small proportion of the overall variation in log DDDs.This study focused only on prescription of all antibiotics, further research around the trends and factors associated with prescription of specific antibiotics, such those prescribed for UTIs which account for a large proportion of prescriptions may be provide important insight and highlight further opportunities for improving antimicrobial stewardship in NI primary care.Finally the findings are produced in the specific context of Northern Ireland's population and its health system, so the findings may not be applicable in other contexts.Our study provides useful information for policy-makers, public health authorities, healthcare systems and primary care prescribers. It also highlights the importance of accounting for clustering within hierarchical data. Overall, the findings suggest females, those in the older age-groups and parents of young children should be the focus of campaigns to reduce antibiotic prescribing in primary care. Some attention should also be paid to ensuring proper management of people with catheters and other comorbidities in line with current guidance. Finally, any campaign to reduce prescribing in primary care should involve GP practices themselves, perhaps in the form of engagement through the NI GP federations.


In China, MgO-based expansive agent (MEA) has been used for concrete shrinkage compensation and cracking control for over 40 years. The expansive behavior of MEA in cementitious materials could be manipulated to some extent by adjusting the calcination process of MEA and influenced by the restraint condition of the matrix. It is key to investigate the factors related to deformation and cracking resistance so that the desired performance of MEA in certain concrete structures could be achieved. This paper reviews the influence of key parameters such as hydration reactivity, dosage, and calcination conditions of MEA, the water-to-binder ratio, supplementary cementitious material, aggregates, and curing conditions on the deformation and cracking resistivity of cement paste, mortar, and concrete with an MEA addition. The numerical simulation methods and deformation prediction models are then summarized and analyzed for more reasonable estimations. In the past 50 years, magnesium oxide has been applied as an expansive agent for concrete shrinkage compensation in massive civil and infrastructure projects in China and other countries . The shrThe factors involved in the deformation and cracking resistance could be classified into three categories: magnesium-oxide-related, cement-related, and curing-condition-related. As for magnesium-oxide-related factors, the dosage and reactivity of MgO are the two main factors that have received much attention and interest. The calcination procedure of magnesium oxide could be represented to some extent by the reactivity of MgO when studying its effect on deformation; however, some research shows insufficient reactivity acquired by using the neutralization method when the sample is a mixture of MgO from varied sources . The infThis paper presents a literature review of the deformation and cracking resistance of MgO-incorporated cementitious materials by analyzing the related factors from three aspects: MgO properties, cement and aggregate, and curing conditions. The relationships between these factors and the deformation or cracking resistance are discussed to determine the possible principles and mechanisms. Meanwhile, the methods and models for the estimation of MgO-incorporated concrete (or paste) deformation are reviewed for understanding the driving force of expansion, which can act as a reference for the application of MgO in novel cementitious systems. Finally, several conclusions are drawn from the analysis, and the discussion reflects the scientific research progress on the deformation and cracking resistance of MgO-incorporated cementitious materials.Magnesium oxide used as an expansive agent in cementitious materials is usually obtained from the calcination of minerals such as magnesite and dolomite that are rich in magnesium carbonate content, with a calcination temperature in the range of 700–1100 °C, and residence time from 0.5 to 2 h. The physical properties of MgO such as particle size distribution, specific surface area, and crystallite size are affected by the calcination temperature, residence time, and cooling rate of the calcination process. With elevated calcination temperatures or prolonged residence time, both the particle size and crystallite size of MgO increase, and the specific surface area of MgO decreases, leading to a reduction in defects ,17. CompAt different ages, the deformation of cementitious materials containing MgO of various reactivity shows different features. As shown in As shown in The addition of MgO is either by partially replacing binders or adding an additive. In Aggregate not only restrains the deformation of concrete mixed with MgO but also causes changes in the water content of the concrete via water absorption. The expansive strain in concrete specimens is about 10%–30% of the strain in the mortar or paste specimens with the same MgO content (by weight of cement) and w/b ratio ,39,40,41The expansion of concrete or mortar mixed with MgO increases with the increase in the w/b ratio ,47,48,49The type of cement could affect the deformation of concrete with MgO. Concrete that incorporates high-magnesia cement could show certain expansive properties. However, its expansion relates to the calcination temperature of cement and mineral compositions rather than the MgO content ,44,52,53Fly ash is a common mineral admixture for concrete that contains MgO. As shown in Increasing the curing temperature can promote the expansive behavior of MgO. As shown in Increasing the curing relative humidity (RH) can also promote the expansion of concrete with MgO. The commonly used curing methods for testing include water curing, sealed curing, RH = 60% (dry shrinkage test), RH = 95% (standard curing), etc. When curing humidity of 60% and 100% is compared, the restrained expansion rate of concrete with MgO increases with RH . CompariDue to its relatively delayed expansion, MgO cannot fully compensate for the early shrinkage of concrete and is often used together with other shrinkage reduction methods. Calcium oxide and calcium sulfoaluminate expansive agents have the characteristics of rapid expansion at early ages . The addThe cracking resistance of concrete with MgO is better than ordinary concrete with the same w/b ratio. To evaluate the cracking resistance, tests are carried out under temperature stress, loading, restraint plastic shrinkage, or drying shrinkage, and the common parameters adopted are tensile strength , elastic modulus, initial cracking time, cracking temperature, and coefficients that are integrations of these parameters. Lei Wang et al.  investig1, a2, b1, and b2 are all derived from fitting the function with experimental ultimate autogenous deformation of concrete with MgO cured at different curing temperatures. Due to the nonlinear relationship between deformation and temperature (or age) in Equation (1), the Newton–Raphson method was adopted for calculation. To validate the model, the strain calculated by using the hyperbolic model with temperature history input from the site was compared with the strain directly obtained from the same test points, and the deviation varied from 14% to 33% [1 relates to the MgO content, and the coefficient k2 relates to the fly ash content [1 and k2 are determined through regression analysis of the experimental results. As shown in 0ε is the ultimate expansion of concrete, and k(m) is the coefficient related to the MgO content. Liu et al. [τ in Equation (3) for possible temperature changes as cementitious materials hydrate, especially in mass concrete. When temperature changes in concrete occur, the equivalent age result is more accurate than the ordinary exponential model. Zhang et al. [The deformation estimation methods for MgO-incorporated concrete mainly include the hyperbolic model, the exponential model, and the tabular interpolation method. In the hyperbolic model, the autogenous deformation of concrete is described as a hyperbolic function of age. As shown in Equation (1) , the tem% to 33% . In Equa content . Both k1u et al.  introducg et al.  also cong et al.  describeg et al. ,82. A la2 in pore space. In Equation (4), the mole balance equation is established assuming that periclase dissolves and brucite forms instantaneously, and the volume change jφ caused by phase j is expressed as the sum of the volume change induced by matrix deformation and the volume of phase j. As shown in Equation (5), the volumetric strain is given, and the drained assumption and absent gradient are taken into account during the calculation. Due to the local growth of Mg(OH)2  and the underestimation of MgO’s solid–liquid interface energy, the calculated strain value is lower than the experimental result. Feng et al. [For chemomechanical models, Lecampion et al.  used porg et al.  develope(1)The influence of MgO on expansive behavior is classified into three aspects: reactivity, content, and incorporation manner of MgO. Cementitious materials with high-activity MgO  show a higher expansive rate and reach constant deformation earlier, while those with low-activity MgO  expand slower but show higher expansion at later ages . The difference in the pattern of deformation evolution relates to the hydration process of MgO. The expansion of cementitious materials increases as the MgO content increases, and MgO used as an additive shows higher expansion than MgO used as replacements for binders in concrete.(2)The effect of concrete matrix on expansive behavior is divided into the w/b ratio, cement composition, and supplementary cementitious materials. When the w/b ratio is lower than 0.45, it promotes the expansion of cementitious materials with MgO, as the increase in the w/b ratio helps to mitigate autogenous shrinkage and provides sufficient free water for MgO hydration. For cementitious materials with a w/b ratio higher than 0.45, expansion decreases as the w/b ratio increases due to the reduced autogenous shrinkage and coarsening of the pore structure. Low-heat cement slows down the hydration process and hydration heat evolution when compared to ordinary and medium-heat cement, resulting in less expansion. With the incorporation of fly ash and slag, the expansion of cementitious material with MgO is reduced, and at the same time, autogenous shrinkage is mitigated. The effect of fly ash and slag has both advantages and disadvantages on deformation, which requires investigation under specific circumstances. In addition, coarse aggregates restrain the concrete matrix to limit deformation and affect the paste through water adsorption.(3)The expansion of cementitious materials with MgO increases as the curing relative humidity rises, and elevated temperature can significantly improve the expansion, especially for low-activity MgO. Water curing at elevated temperatures is the most effective method for promoting expansion among all the curing conditions.(4)The cracking resistance of cementitious materials is improved when MgO is added as an expansive agent. The addition of MgO can improve tensile strength and reduce the cracking temperature of cementitious materials during the cooling process.(5)The methods for estimating the deformation of concrete or paste containing MgO are the hyperbolic model, the exponential model, and the tabular interpolation method. With certain revisions to these methods, such as introducing the equivalent age and activation energy of MgO, the predicted results can reach a reasonable level of accuracy when a considerable number of experimental data have been input. Chemomechanical models, though not thoroughly investigated, are essential for uncovering the relationship between the hydration of MgO and the expansion of cementitious materials.(6)There are several issues related to the deformation of cementitious materials that are still under debate or have not been explored. Supplementary cementitious materials such as silica fume, glass powder, and other common materials in concrete may alter the chemistry of the matrix and pore solution, which can exert an impact on MgO’s expansive behavior. Though the correlation between the specific surface area (reaction time) of MgO and the dissolution rate has been established, the quantitative relationship between the hydration process of MgO and the expansive deformation of concrete is yet to be determined, as the driving force of expansion is under debate. Furthermore, with the study of MgO hydration in cementitious systems in terms of both the kinetics and thermodynamic aspects and the influence of MgO on the microstructure of the matrix, it would be clear to determine the chemomechanical process during hydration and establish a model for the prediction and optimization of the deformation of MgO-incorporated cementitious materials.Several conclusions can be drawn from our review of the literature on the deformation and cracking resistance of MgO-incorporated cementitious materials:


An inflammatory pseudotumor is a benign disease characterized by tumor-like lesions consisting of inflammatory cells including plasma cells and fibrous tissue. Recently, some inflammatory pseudotumor cases proved to be a form of Immunoglobulin G4-related disease (IgG4-RD). This novel clinical entity, recognized as a fibroinflammatory condition, is characterized by lymphoplasmacytic infiltration with a predominance of IgG4-positive plasma cells, storiform fibrosis, and often elevated serum IgG4 concentrations. We report a case of IgG4-RD in the form of an inflammatory pseudotumor in the liver with combined sclerosing cholangitis. We recommend that for diagnosing IgG4-RD accurately, it is important to obtain adequate tissue samples and follow-up the lesion in clinical practice. Klebsiella pneumoniae and E. coli [An inflammatory pseudotumor is characterized by tumor-like lesions consisting of inflammatory cells and fibrous tissue. An inflammatory pseudotumor was first described in the lung , but is  E. coli ,3 and vi E. coli , or the IgG4-RD is a novel clinical entity recognized as a fibroinflammatory condition, characterized by lymphoplasmacytic infiltration with a predominance of IgG4-positive plasma cells, storiform fibrosis, and often elevated serum IgG4 concentrations . IgG4-RDThis paper reports the case of IgG4-RD of the liver and bile ducts presenting as an inflammatory pseudotumor. 3/µL), elevated aspartate transaminase (128 U/L (reference: ≤40)), elevated alanine transaminase (96 U/L (reference: ≤41)), elevated alkaline phosphatase (180 U/L (reference: 40–129)), elevated gamma-glutamyltransferase (132 U/L (reference: 10–71)), and slightly elevated total bilirubin (1.8 mg/dL (reference: <1.2)). He was diagnosed with acute cholangitis and he had stones removed from the common bile duct. Following laparoscopic cholecystectomy, pain in RUQ and back developed. Computed tomography (CT) showed a newly developed 6 cm-sized mass in segments 6 and 7 of the liver as compared with CT scan images before cholecystectomy  pain. His laboratory findings showed elevated white blood cell counts (11.2 (reference: 4.8–10.8) × 10stectomy . He was stectomy . The hepOn the 6-month follow-up liver dynamic CT A–C, therWe hypothesized that there might be biliary strictures causing upstream bile duct dilatation, recurrent cholangitis, and consequently a liver abscess. Due to claustrophobia, the patient did not undergo magnetic resonance imaging. A US-guided right posterior bile duct access cholangiography was done to explore the lesion and perform therapeutic bile drainage with recanalization. However, this trial failed, showing focal tortuous distension of the bile duct with outflow obstruction D. We decWe reviewed the pathology of the resected liver with hematoxylin & eosin staining A–C. DiffAfter liver resection, the patient started taking 0.5 mg/kg prednisolone once a day. However, he complained of moon face and was allergic to azathioprine substituting for prednisolone; thus, we discontinued these medications. He underwent periodic laboratory and imaging tests. The 6-month follow-up CT showed no remnant of the mass nor newly developed bile duct dilatation or masses. Informed consent was obtained from the patient regarding the publication of this case report. To our knowledge, this is the first report of a case of abrupt onset and progression of an inflammatory pseudotumor caused by IgG4-RD involving the liver and bile ducts. There have been some reported cases of IgG4-related hepatic inflammatory pseudotumors or IgG4-related sclerosing cholangitis (IgG4-SC) mimicking cholangiocarinoma ,11,12. HIn addition, in our case, the patient’s newly developed mass was biopsied. Prior to biopsy, it looked like a mass-forming intrahepatic cholangiocarcinoma with bile duct dilatation. This mass lesion had abruptly developed in one month. However, pathology of 3 pieces measuring 1.5 cm in length each, showed benign lesions with non-specific inflammation around the bile duct. In this case, serum IgG4 was not elevated after resection. It could have been in the middle of falling or the initial serum IgG4 level was in a normal range. It has been recently recognized that serum IgG4 levels are not elevated in a substantial percentage of patients diagnosed as IgG4-RD and serum IgG4 elevation is no longer considered essential to the diagnosis of IgG4-RD . In an IBased on the recent introduction of a novel clinical entity of IgG4-RD, it draws more attention and makes the diagnostic rate higher. Even if histological findings are necessary to diagnose IgG4-RD, it is sometimes difficult to obtain adequate tissue samples. In our case, although needle biopsy was performed by an expert to obtain 3 tissue samples, it showed no evidence of IgG4-RD. The reason might be that the lesion was at a very early stage of development, showing heterogeneity. Thus, if a mass is suspicious of a benign inflammatory and fibrous lesion, immunohistochemical staining for IgG and IgG4 should be done to exclude IgG4-RD.We followed the case of IgG4-RD manifesting as a hepatic inflammatory pseudotumor diagnosed and resolved by hepatic resection with histopathological examination. In conclusion, it is important to suspect IgG4-RD for mass lesion early and to diagnose IgG4-RD accurately by obtaining adequate tissue samples and following-up the lesion.