Protracted outbreaks of VIM-producing Pseudomonas aeruginosa in a surgical intensive care unit in France, January 2018 to June 2024.

Background: Pseudomonas aeruginosa is frequently responsible for hospital-acquired infections. It may be isolated in healthcare environment where it can survive. Between January 2018 and June 2024, a growing number of VIM-producing Pseudomonas aeruginosa (PA-VIM) were isolated from patients hospitalized in our surgical intensive care unit (SICU). The aim of this study was to investigate SICU long-term PA-VIM outbreaks involving a persistent environmental reservoir.

Methods: Investigations included an active case finding, a matched case-control study to identify factors associated with PA-VIM acquisition, the identification of environmental reservoirs, a whole-genome sequencing analysis of patient and environmental strains, and the implementation of control measures.

Results: During these outbreaks, 32 patients were colonized or identified with at least one PA-VIM positive clinical sample during their SICU stay. Factors significantly associated with the PA-VIM acquisition in the conditional univariate analysis included exposure to antibiotics (e.g., carbapenem) and antifungals, and the use of a nasogastric tube and enteral nutrition. Among 342 environmental samples collected in the SICU (including sink drains, syringes and glasses containing syringes used for enteral nutrition), 67 (19.6%) were found positive for PA-VIM. Core-genome Multi-Locus Sequence Typing analysis identified 2 major clones, each including patients and environmental strains.

Conclusions: These long-lasting outbreaks of PA-VIM were associated to a persistent environmental contamination of sink drains. All the strategies aiming at eradicating PA-VIM reservoirs (disinfection, descaling, or replacement of sink drains) failed or only showed a temporary effect.