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 multidrug-resistant pathogenic bacteria.

Aim: 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 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 who 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 multi-locus sequence typing analysis of all genomes, 15 clusters of highly related isolates were identified, of which seven included 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.