Decline of Antimicrobial Resistance in Pseudomonas aeruginosa Bacteremia Following the COVID-19 Pandemic: a Longitudinal Observational Study
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Background
Multidrug-resistant Pseudomonas aeruginosa (MDRPA) poses significant challenges in hospital settings. Understanding the effects of the unprecedented changes brought by the COVID-19 pandemic on antimicrobial resistance in P. aeruginosa (PA) is essential to inform stewardship efforts. This study investigated the dynamics of antimicrobial resistance in PA bacteremia after the start of the pandemic.
Methods
This single-centre retrospective cohort study included adult inpatients with PA bacteraemia at the University Hospital Zurich between January 2014 and December 2023. Data were retrieved from electronic records. The primary outcome was the association between the start of the COVID-19 pandemic and PA with MDR, defined as resistance to ≥3 of 5 antibiotic classes. We used logistic regression to adjust for age, sex and ICU treatment, accounting for multiple bacteremia instances within the same patient using cluster-robust standard errors. Secondary outcomes included changes in resistance patterns and patient demographics, with antimicrobial exposure assessed as median monthly days of therapy (DOT).
Results
A total of 493 instances of PA bacteremia in 333 patients were observed during the study period. The proportion of MDRPA declined from 21% (62/291) pre-pandemic to 9% (19/202) post-pandemic (adjusted OR 0.38, 95% CI 0.18–0.79, p=0.01). The occurrence of MDRPA during hospitalisation following an initial instance of non-MDRPA bacteremia was rare and unlikely to happen earlier than after two weeks. Antimicrobial consumption patterns shifted after the start of the pandemic, with reduced use of amikacin and ciprofloxacin and increased use of cefepime and meropenem. Overall inhospital-mortality among patients with MDRPA bacteraemia remained high (28%), with no substantial differences before and after the pandemic (adjusted hazard ratio 1.57, 95% CI 0.43–5.67, p=0.49).
Conclusion
We observed a decline in MDRPA occurrence after the start of the COVID-19 pandemic, possibly driven by intensified infection control measures, shifts in antimicrobial use, and changes in patient populations.
