Surveillance of temporal trends and antimicrobial resistance in nosocomial respiratory pathogens, Switzerland, 2007 to 2024

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.