Aquatic reservoir-associated outbreaks of multi-drug-resistant bacteria: a hospital outbreak report of Pseudomonas aeruginosa in perspective from the Dutch national surveillance databases

Abstract

Background: Water fixtures can be involved in hospital outbreaks with multi-resistant pathogens.

Aim: To document an outbreak of a Verona integron-encoded metallo-β-lactamase type 2-producing carbapenem-resistant Pseudomonas aeruginosa (CRPA-VIM) and evaluate infection control measures. Additionally, to overview waterborne outbreaks involving multi-resistant pathogens in Dutch healthcare institutions.

Methods: Epidemiologic analysis, selective culturing, PCR, and whole-genome sequencing (WGS) identified the outbreak sources. National surveillance databases were consulted.

Findings: In December 2023, three ICU patients tested positive for CRPA-VIM with multi-locus sequence type (MLST) ST111. Contaminated sinks were identified as the source. Despite interventions, a new cluster of five CRPA-VIM-positive patients emerged in March-April 2024. WGS linked this to a decommissioned sink (November 2021) and two patients (December 2021 and April 2023). Contact tracing and source investigations found no interpatient transmission; sinks were identified as the sole source. Measures, including contact precautions, intensified cleaning and hygiene procedures, retraining, installing and frequently replacing splash- and aerosol-reducing inlets, and faucet modifications failed to halt the transmission. No new cases occurred after the removal of all water fixtures in the ICU patient rooms. The outbreak strain was unique to the hospital and showed no genetic clustering in the national surveillance. Nationally, three to five waterborne outbreaks with highly resistant micro-organisms in hospitals are reported annually.

Conclusions: CRPA-VIM was transmitted from sinks to ICU patients without interpatient transmission. Infection control requires comprehensive surveillance of patients and the environment. A water-restricted and drain-free environment ended the outbreak. Future hospital design should minimize contamination from drains and sinks to reduce the nosocomial infection risk.

Keywords: Aquatic reservoir; Carbapenem-resistant; Carbapenemase; Highly resistant micro-organisms; Hospital design; Multi-drug-resistant bacteria.