Sink drains as reservoirs of VIM-2 metallo-β-lactamase-producing Pseudomonas aeruginosa in a Belgian intensive care unit: relation to patients investigated by whole genome sequencing

Background: Hospital acquired infections caused by VIM encoded metallo-β-lactamase-positive Pseudomonas aeruginosa are a major problem in intensive care units (ICUs) worldwide. A previous study conducted in the UZ Brussel hospital revealed that sink drains of the ICU were a possible source of various multi-drug resistant pathogenic bacteria.

Aim: We aimed to investigate the presence and persistence of VIM P. aeruginosa in the sink drains of the four adult ICUs and their role in nosocomial infections emphasizing a sink-to-patient transmission.

Methods: Thirty-six sinks located in the ICUs of the UZ Brussel were sampled and screened for the presence of VIM P. aeruginosa in August and October 2019. Whole genome sequencing (WGS) was performed on all positive sink drain isolates together with 61 isolates from patients that were retrospectively selected (ICU patients 2019-2020, n=46; non-ICU patients 2019, n=6).

Findings: Twenty sinks were found positive for P. aeruginosa at both sampling time points. WGS revealed that the predominating environmental cluster belonged to sequence type ST111. Ten additional STs were identified. VIM-2 was detected among all ST17 (n=2) and ST111 (n=14) sink drain isolates. Based on whole-genome multilocus sequence typing analysis of all genomes, 15 clusters of highly related isolates were identified, of which seven include both sink drain and clinical isolates.

Conclusion: Our findings confirm that sink drains are a possible source of VIM-2 P. aeruginosa, probably after being contaminated with clinical waste from patients. Patients could be exposed to VIM-2 P. aeruginosa dispersed in their environment because of colonized sink drains.