BACKGROUND Hospital-acquired pneumonia is a common nosocomial infection, frequently caused by multidrug-resistant organisms. However, no systematic surveillance data exist on respiratory bacteria in Switzerland. AIM This laboratory-based surveillance study analysed temporal trends in the incidence and antimicrobial resistance (AMR) of nosocomial respiratory bacteria in Swiss hospitals. METHODS A retrospective analysis using data from the Swiss Centre for Antibiotic Resistance from 2007 to 2024 focused on meticillin-resistant Staphylococcus aureus (MRSA), third-generation cephalosporin-resistant (3GCR) Enterobacterales, carbapenem-resistant Enterobacterales, carbapenem-resistant Pseudomonas aeruginosa and carbapenem-resistant Acinetobacter spp. Data were compared across the periods 2007–2015 and 2016–2024. Temporal trends in pathogen incidence and AMR were assessed using Poisson regression models. RESULTS We included 46,374 respiratory isolates. For respiratory bacteria incidence, difficult to treat Enterobacterales such as Serratia spp. increased significantly in the later vs the earlier period, as reflected by a higher adjusted incidence rate ratio (aIRR: 1.14, 95% confidence interval (CI): 1.06–1.23, p < 0.001). Regarding important pathogen-specific AMR, MRSA (aIRR: 0.78, 95% CI: 0.66–0.91, p = 0.002) and 3GCR Enterobacterales (aIRR: 0.81, 95% CI: 0.75–0.87, p < 0.001) incidence decreased in the later period. In contrast, carbapenem resistance in Enterobacterales (aIRR: 3.27, 95% CI: 2.43–4.46, p < 0.001), P. aeruginosa (aIRR: 2.68, 95% CI: 2.33–3.10, p < 0.001) and Acinetobacter spp. (aIRR: 1.82, 95% CI: 1.15–2.95, p = 0.01) was higher in the later period. CONCLUSIONS While MRSA and 3GCR Enterobacterales incidence declined, carbapenem-resistant Gram-negative bacteria incidence increased, underscoring the need for strengthened surveillance.

Antimicrobial resistance (AMR) surveillance requires approaches that monitor both clinical and community-level dynamics. We monitored antibiotic-resistant bacteria in Swiss wastewater and compared these results with human resistance and antibiotic consumption data from the national surveillance network of the Swiss Center for Antibiotic Resistance (ANRESIS). Between 2021 and 2024, 772 samples from six wastewater treatment plants were analyzed for Escherichia coli, extended-spectrum β-lactamase-producing (ESBL)-E. coli, carbapenem-resistant E. coli (CR-E. coli), Enterococcus faecium/faecalis, and vancomycin-resistant enterococci (VRE). The rank order of the proportion of resistance was conserved between wastewater and clinical data. Mean (±standard deviation) wastewater resistance percentages were 2.2 ± 0.8 for ESBL-E. coli, 0.4 ± 0.6 for VRE, and 0.1 ± 0.1 for CR-E. coli. Clinical resistance percentages were 9.8 ± 0.8 for ESBL-E. coli, 2.9 ± 1.4 for VRE, and 0.3 ± 0.1 for CR-E. coli. Both data sets showed similar rising trends for ESBL-E. coli and VRE, while CR-E. coli remained stable in wastewater but increased slightly in clinics. No consistent lead-lag relationships were observed between wastewater resistance, clinical resistance, or antibiotic use, indicating independent short-term dynamics. Resistance percentages in wastewater were not associated with antibiotic use data for either the antibiotics used for treatment or the ones that are selective for the target. These results suggest that wastewater monitoring reflects long-term population-level AMR dynamics, aligning with clinical trends over years but not months.

We conducted a retrospective analysis of Citrobacter spp. surveillance data from acute care hospitals that contributed Citrobacter spp. data to the national surveillance system ANRESIS from January 2010 to December 2022. The incidence of Citrobacter spp. bloodstream infections (BSIs) in Switzerland was calculated, as well as the proportion of Citrobacter spp. isolates from urinary tract samples. We also evaluated the susceptibility of Citrobacter spp. isolates to clinically important antibiotics. From 2010 to 2022, there were 33,958 Citrobacter spp. from patients across 55 acute care hospitals continuously participating in ANRESIS included in this analysis. We observed an annual increase in the number of Citrobacter spp. BSIs, from 2.5 to 4.2 cases per 100,000 patient days (IRR: 1.04, 95% CI: 0.96–1.12). We found a higher incidence among male versus female patients (IRR: 2.47, 95% CI: 1.28–4.74) and in those aged ≥65 years, as compared with younger patients (IRR: 2.26, 95% CI: 1.18–4.32). The proportion of Citrobacter spp. among positive urinary tract samples also increased (from 18.6 to 24.7 per 1000 samples). Among ICU patients, there was a considerable proportion of resistance to third-generation cephalosporins among C. freundii isolates (26.8–44.0%), compared with non-freundii isolates (1.7–6.9%). Citrobacter spp. is gaining clinical importance in Switzerland; further studies are needed to better understand the underlying mechanisms.

We describe the emergence of vancomycin-resistant Enterococcus faecium (VREfm) vanA ST612 in Switzerland from 2018 to 2024 that resulted in a national outbreak investigation. This clone has predisposing genetic alterations associated with reduced daptomycin susceptibility. The National Nosocomial Outbreak Investigation Center was commissioned to assess the temporospatial distribution of this clone in Switzerland and evaluate its clinical impact. Core genome multi-locus sequence typing (cgMLST) revealed five separate VREfm vanA ST612 clusters of different sizes across different healthcare regions, but predominantly in the German-speaking part. The broad geographic dissemination and temporal variation in detection suggests multiple introductions to the healthcare system. One of these cgMLST clusters (n = 79 cases) with an infection rate of 12.8% was ongoing, mainly affecting patients with extensive contact to the Swiss healthcare system or prior antibiotic exposure. The detection of daptomycin non-susceptibility in patients without prior daptomycin exposure suggests ongoing E. faecium adaptation due to external pressures. Future prevention efforts should emphasise assessing barriers for active surveillance cultures, developing a national standard for cost-effective sequencing methods and promoting the sharing of sequencing results together with epidemiological metadata. Our report intends to raise awareness as this sequence type might already be spreading undetected in European countries.

Background:Studies relating the usage of antibiotics with extended-spectrum cephalosporin resistance (ESC-R) rates from clinical isolates in nursing homes (NHs) are rare. We investigated associations between the intensity of NH-level antibiotic consumption (ABC) and the frequency of ESC-R expressing urinary Escherichia coli, Klebsiella spp. and Proteus spp. isolates from NH residents. Materials and methods:We used retrospective data on ABC and ESC-R counts aggregated by NH and year between 2017 and 2022 from NHs of canton Vaud in Switzerland. Negative binomial regression was used to relate ABC intensity, expressed as DDDs per 1000 resident days, with counts of ESC-R expressing bacteria. Results:Fifty-four NHs were included cumulatively accounting for 6601 urinary isolates, of which 5028 E. coli, 999 Klebsiella spp. and 574 Proteus spp. Among these, the 6-year ESC-R cumulative incidence was 10.3% (E. coli 12.6%, Klebsiella spp. 3.8% and Proteus spp. 1.2%). Median annual overall ABC varied between 31.3 and 44.2 DDDs per 1000 resident days. There was no association between overall ABC, most antibiotic categories and ESC-R cumulative incidence. The consumption of cephalosporins [adjusted incidence rate ratio (aIRR): 1.023, 95% CI: 1-1.047] and carbapenems (aIRR: 1.542, 95% CI: 1.018-2.336) was independently associated with increased incidence. Conclusion:No association was found between overall ABC and ESC-R rates. Cephalosporin consumption showed a modest association, while for carbapenems this could reflect therapeutic use. These findings highlight the need for enhanced surveillance and resident-level data to better understand antibiotic resistance drivers in this setting.

Bloodstream infections (BSIs) cause significant morbidity and mortality worldwide. Pseudomonas aeruginosa is an important microorganism in BSIs. The aim of this study was to analyze recent trends in the incidence and resistance rates of P. aeruginosa BSIs in Switzerland and its different linguistic regions. This retrospective, nationwide observational study analyzed the incidence (using Poisson regression models) and antimicrobial resistance (using logistic regression models) of P. aeruginosa BSIs in Switzerland from 2010 to 2022. The annual incidence of P. aeruginosa BSIs in Switzerland increased from 5.5 BSIs per 100,000 inhabitants in 2010 to 7.6 BSIs per 100,000 inhabitants in 2022 (p < 0.001). The incidence was higher in the French-speaking region than in the German-speaking region. The resistance rates increased significantly for cefepime (2.4

Background:Clostridioides difficile infection (CDI) is a common gastrointestinal disease in healthcare settings, ranging from uncomplicated diarrhoea to life-threatening pseudomembranous colitis. It is associated with increased morbidity, mortality and healthcare costs. The aim of the study was to correlate CDI incidence with total and specific antibiotic consumption across 17 clinical departments of an academic hospital. Methods:This retrospective correlation study used data on CDI and antibiotic prescriptions from 1.1.2008 to 31.12.2021. CDI episodes were defined using CDC criteria. Antibiotic consumption was reported per WHO in defined daily doses (DDD). A mixed effects logistic regression model was fitted with each department as random effect to determine CDI incidence as a function of year and adjusted for antibiotic consumption. Results:Amoxicillin-clavulanate showed the highest annual consumption across the 17 departments (median 13.5 DDD/100 patient-days). The average CDI incidence was highest in nephrology (22.3/10'000 patient-days) and lowest in otorhinolaryngology (0.1/10'000 patient-days). We observed an association between overall antimicrobial consumption and CDI incidence (incidence risk ratio (IRR) per 10 DDD/100 patient-days of 1.16, 95% confidence interval (1.09, 1.23), P<0.001). When plotting each department's CDI incidence against the departmental average annual consumption, no significant trend was found; however, there was a trend for the association between CDI and selected antibiotic usage, such as carbapenems (P=0.003), ceftriaxone (P=0.04), cefepime (P<0.001), macrolides (P<0.001) and piperacillin/tazobactam (P=0.03). Conclusions:We detected an association between antibiotic consumption and CDI incidence across the departments of an academic hospital; however, we could only correlate departmental CDI incidence with the usage of select antibiotics.

To reduce antimicrobial resistance (AMR), pathogen-specific AMR burden data are crucial to guide target selection for research and development of vaccines and monoclonal antibodies (mAbs). We identified knowledge gaps through previously conducted systematic reviews, which informed a Delphi expert consultation on future AMR research priorities and harmonisation strategies to support data-driven decision-making. Consensus (≥80% agreement) on importance and feasibility of research topics was achieved in two rounds, involving 24 of 39 and 19 of 24 invited experts, respectively. Priority pathogens and resistance profiles for future research were identified: third generation cephalosporin-resistant Klebsiella pneumoniae and Escherichia coli, for bloodstream and urinary tract infections, respectively, and meticillin-resistant Staphylococcus aureus for surgical-site infections. Prioritised high-risk populations included surgical, haemato-oncological and transplant patients. Mortality and resource use were prioritised as health-economic outcomes. The importance of age-stratified data and inclusion of a non-infected comparator group were highlighted. This agenda provides guidance for future research to fill knowledge gaps and support data-driven selection of target pathogens and populations for new preventive and treatment strategies, specifically vaccines and mAbs, to effectively address the AMR burden in Europe. These research priorities are also relevant to improve the evidence base for future AMR burden estimates.

Background: The association between the COVID-19 pandemic and the incidence of invasive infections caused by multidrug-resistant organisms remains a topic of debate. Aim: To analyse the national incidence rates of bloodstream infections (BSI) caused by Escherichia coli (EC) and Klebsiella pneumoniae (KP) with extended-spectrum cephalosporin resistance (ESCR) in two distinct regions in Switzerland, each exhibiting varying antimicrobial resistance patterns and that were impacted differently by the pandemic. Methods: Data was analysed from positive blood cultures prospectively collected by the nationwide surveillance system (ANRESIS) from January 1 st , 2015, to August 31 st , 2022. To explore the potential relationship between COVID-19 patient occupancy and ESCR incidence rates, an in-depth analysis was conducted over the two-year pandemic period from April 1 st , 2020, to March 30 th , 2022, using Quasi-Poisson and logistic regression analyses. Findings: During the study period, 40,997 EC-BSI and 8537 KP-BSI episodes were collected and reported to ANRESIS by the participating hospitals. ESCR was observed in 11% ( N = 4313) of E. coli and 8% ( N = 664) of K. pneumoniae , respectively. A significant reduction in ESCR-EC BSI incidence occurred during the pandemic in the region with the highest COVID19 incidence. Conversely, ESCR-KP BSI incidence initially fell considerably and then increased during the pandemic in both regions, though this effect was not statistically significant. No association between hospital occupancy from COVID-19 patients and these trends was observed.

Background The COVID-19 pandemic has been a challenge for health-care systems and antibiotic stewards as uncertainty regarding treatment and bacterial coinfections raised concern. Methods This retrospective observational study examined the association of the pandemic on outpatient antibiotic sales and prescriptions in Switzerland using interrupted time series (ITS) analyses. Data from IQVIA™ and the Sentinella Network were used to analyze antibiotic consumption and prescription patterns over a 72-month period from January 2018 to December 2023, divided into pre-pandemic, pandemic, and post-pandemic periods. Results Antibiotic consumption decreased during the pandemic and returned to pre-pandemic levels in the post-pandemic period. A decrease in level was most pronounced in the French-speaking region (−2.82 defined daily doses per 1,000 inhabitants per day (DID) per month, 95 %CI [−4.34, −1.30], p < 0.001) and the Italian-speaking region (−2.80 DID per month, 95 %CI [−4.78, −0.82], p < 0.01), followed by the German-speaking region (−1.72 DID per month, 95 %CI [−2.71, −0.74], p < 0.01). Similarly, in the ITS, the relative change of model estimates in antibiotic prescriptions by GPs and pediatricians for upper respiratory tract infections, was of −36.0 % and −50.3 % resp. in the pandemic period and +10.1 % and −2.6 % in the post-pandemic period compared with the pre-pandemic period. Conclusions A decrease of antibiotic prescriptions was observed in GPs and pediatricians during the COVID-19 pandemic, followed by a return to pre-pandemic levels. The patterns in antibiotic prescriptions aligned with the epidemiology of respiratory infections and demonstrated a pronounced association with the implementation and subsequent removal of non-pharmaceutical interventions.

Background In Europe and other high-income countries, antibiotics are mainly prescribed in the outpatient setting, which consists of primary, specialist and hospital-affiliated outpatient care. Established surveillance platforms report antimicrobial consumption (AMC) on aggregated levels and the contribution of the different prescriber groups is unknown. Aim To determine the contribution of different prescribers to the overall outpatient AMC in Switzerland. Methods We conducted a retrospective observational study using claims data from one large Swiss health insurance company, covering the period from 2015 to 2022. We analysed antibiotic prescriptions (ATC code J01) prescribed in the Swiss outpatient setting. Results were reported as defined daily doses per 1,000 inhabitants per day (DID) and weighted according to the total population of Switzerland based on census data. Results We analysed 3,663,590 antibiotic prescriptions from 49 prescriber groups. Overall, AMC ranged from 9.12 DID (2015) to 7.99 DID (2022). General internal medicine (40.1% of all prescribed DID in 2022), hospital-affiliated outpatient care (20.6%), group practices (17.3%), paediatrics (5.4%) and gynaecology (3.7%) were the largest prescriber groups. Primary care accounted for two-thirds of the prescribed DID. Quantity and type of antibiotics prescribed varied between the prescriber groups. Broad-spectrum penicillins, tetracyclines and macrolides were the most prescribed antibiotic classes. Conclusion Primary care contributed considerably less to AMC than anticipated, and hospital-affiliated outpatient care emerged as an important prescriber. Surveillance at the prescriber level enables the identification of prescribing patterns within all prescriber groups, offering unprecedented visibility and allowing a more targeted antibiotic stewardship according to prescriber groups.

Antimicrobial resistance comes with high morbidity and mortality burden, and ultimately high impact on healthcare and social costs. Efficient strategies are needed to limit antibiotic overuse. This paper investigates the cost-effectiveness of testing patients with lower respiratory tract infection with procalcitonin, either at the point-of-care only or combined with lung ultrasonography. These diagnostic tools help detect the presence of bacterial pneumonia, guiding prescription decisions. The clinical responses of these strategies were studied in the primary care setting. Evidence is needed on their cost-effectiveness. We used data from a cluster-randomized bi-centric clinical trial conducted in Switzerland and estimated patient-level costs using data on resource use to which we applied Swiss tariffs. Combining the incremental costs of the two strategies and the reduction in the 28-days antibiotic prescription rate (APR) compared to usual care, we calculated Incremental Cost-Effectiveness Ratios (ICER). We also used the Cost-Effectiveness Acceptability Curve as an analytical decision-making tool. The robustness of the findings is ensured by Probabilistic Sensitivity Analysis and scenario analysis. In the base case scenario, the ICER compared to usual care is 2.3 per percentage point (pp) reduction in APR for the procalcitonin group, and4.4 for procalcitonin-ultrasound combined. Furthermore, we found that for a willingness to pay per patient of more than 2 per pp reduction in the APR, procalcitonin is the strategy with the highest probability to be cost-effective. Our findings suggest that testing patients with respiratory symptoms with procalcitonin to guide antibiotic prescription in the primary care setting represents good value for money.

Antibiotics are often only available in predefined pack sizes, which may not align with guideline recommendations. This can result in leftover pills, leading to inappropriate self-medication or waste disposal, which can both foster the development of antibiotic resistance. The magnitude of inappropriate pack sizes is largely unknown. The objective of this study was to evaluate the potential non-conformity of prescribed antibiotic pack sizes. This retrospective observational study was based on claims data from a large Swiss health insurance company. The study analysed the prescriptions of eleven different antibiotic substances recommended for the five most common indications for antibiotics in Switzerland. All prescriptions for adult outpatients issued by general practitioners in 2022 were included and extrapolated to the entire Swiss population. Potential non-conformity was defined as a mismatch between the total dosage in a pack and the total dosage recommended. A total of n = 947,439 extrapolated prescriptions were analysed. In 10 of 23 of all analysed substance/indication combinations none of the prescribed packs aligned with the respective guideline recommendation. Considering pack sizes in which the total prescribed dosage of a substance did not correspond to any of the total dosages recommended in at least one of the guidelines, 31.6

Scope: Pseudomonas aeruginosa, a ubiquitous opportunistic pathogen considered one of the paradigms of antimicrobial resistance, is among the main causes of hospital -acquired and chronic infections associated with significant morbidity and mortality. This growing threat results from the extraordinary capacity of P. aeruginosa to develop antimicrobial resistance through chromosomal mutations, the increasing prevalence of transferable resistance determinants (such as the carbapenemases and the extendedspectrum fi-lactamases), and the global expansion of epidemic lineages. The general objective of this initiative is to provide a comprehensive update of P. aeruginosa resistance mechanisms, especially for the extensively drug -resistant (XDR)/difficult-to-treat resistance (DTR) international high -risk epidemic lineages, and how the recently approved fi-lactams and fi-lactam/fi-lactamase inhibitor combinations may affect resistance mechanisms and the definition of susceptibility profiles. Methods: To address this challenge, the European Study Group for Antimicrobial Resistance Surveillance (ESGARS) from the European Society of Clinical Microbiology and Infectious Diseases launched the 'Improving Surveillance of Antibiotic -Resistant Pseudomonas aeruginosa in Europe (ISARPAE)' initiative in 2022, supported by the Joint programming initiative on antimicrobial resistance network call and included a panel of over 40 researchers from 18 European Countries. Thus, a ESGARS-ISARPAE position paper was designed and the final version agreed after four rounds of revision and discussion by all panel members. Questions addressed in the position paper: To provide an update on (a) the emerging resistance mechanisms to classical and novel anti-pseudomonal agents, with a particular focus on fi-lactams, (b) the susceptibility profiles associated with the most relevant fi-lactam resistance mechanisms, (c) the impact of the novel agents and resistance mechanisms on the definitions of resistance profiles, and (d) the globally expanding XDR/DTR high -risk lineages and their association with transferable resistance mechanisms. Implication: The evidence presented herein can be used for coordinated epidemiological surveillance and decision making at the European and global level. Antonio Oliver, Clin Microbiol Infect 2024;30:469 (c) 2023 The Authors. Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases. This is an open access article under the CC BY -NC -ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Background: Cassini et al. (2019) estimated that, in 2015, infections with 16 different antibiotic-resistant bacteria resulted in ca 170 disability-adjusted life -years (DALYs) per 100,000 population in the European Union and European Economic area (EU/EEA). The cor-responding estimate for Switzerland was about half of this (87.8 DALYs per 100,000 population) but still higher than that of several EU/EEA countries (e.g. neighbouring Austria (77.2)). Aim: In this study, the burden caused by the same infections due to antibi-otic-resistant bacteria ('AMR burden') in Switzerland from 2010 to 2019 was estimated and the effect of the factors 'linguistic region' and 'hospital type' on this estimate was examined. Methods: Number of infec-tions, DALYs and deaths were estimated according to Cassini et al. (2019) whereas separate models were built for each linguistic region/hospital type combina-tion. Results: DALYs increased significantly from 3,995 (95% uncertainty interval (UI): 3;327-4,805) in 2010 to 6,805 (95% UI: 5,820-7,949) in 2019. Linguistic region and hospital type stratifications significantly affected the absolute values and the slope of the total AMR burden estimates. DALYs per population were higher in the Latin part of Switzerland (98 DALYs per 100,000 population; 95% UI: 83-115) compared with the German part (57 DALYs per 100,000 population; 95% UI: 49-66) and in university hospitals (165 DALYs per 100,000 hospitalisation days; 95% UI: 140-194) compared with non-university hospitals (62 DALYs per 100,000 hospitalisation days; 95% UI: 53-72). Conclusions: The AMR burden estimate in Switzerland has increased significantly between 2010 and 2019. Considerable differences depending on the linguistic region and the hospital type were identified - a find-ing which affects the nationwide burden estimation.

Guidelines recommend chest X-rays (CXRs) to diagnose pneumonia and guide antibiotic treatment. This study aimed to identify clinical predictors of pneumonia that are visible on a chest X-ray (CXR+) which could support ruling out pneumonia and avoiding unnecessary CXRs, including oxygen saturation. A secondary analysis was performed in a clinical trial that included patients with suspected pneumonia in Swiss primary care. CXRs were reviewed by two radiologists. We evaluated the association between clinical signs (heart rate > 100/min, respiratory rate ≥ 24/min, temperature ≥ 37.8 °C, abnormal auscultation, and oxygen saturation < 95%) and CXR+ using multivariate analysis. We also calculated the diagnostic performance of the associated clinical signs combined in a clinical decision rule (CDR), as well as a CDR derived from a large meta-analysis (at least one of the following: heart rate > 100/min, respiratory rate ≥ 24/min, temperature ≥ 37.8 °C, or abnormal auscultation). Out of 469 patients from the initial trial, 107 had a CXR and were included in this study. Of these, 26 (24%) had a CXR+. We found that temperature and oxygen saturation were associated with CXR+. A CDR based on the presence of either temperature ≥ 37.8 °C and/or an oxygen saturation level < 95% had a sensitivity of 69% and a negative likelihood ratio (LR−) of 0.45. The CDR from the meta-analysis had a sensitivity of 92% and an LR− of 0.37. The addition of saturation < 95% to this CDR increased the sensitivity (96%) and decreased the LR− (0.21). In conclusion, this study suggests that pulse oximetry could be added to a simple CDR to decrease the probability of pneumonia to an acceptable level and avoid unnecessary CXRs.