VIM-Positive Pseudomonas aeruginosa Sink Colonization Dynamics in Patient Rooms of a Dutch Tertiary-Care Hospital

Abstract

Background: In hospitals, Verona integron-encoded metallo-β-lactamase (VIM)–positive Pseudomonas aeruginosa (VPPA) frequently colonize sink drains. Sink use has been shown to disperse VPPA to other surfaces surrounding sinks, creating a potential transmission source. Objective: Because VPPA have been isolated from sinks and patients within our hospital, we analyzed colonization dynamics in 2 sinks identified as VPPA hot spots between 2012 and 2018. Methods: One sink was in an intensive care unit (ICU) patient room and the other was in a gastrointestinal surgery (GIS) patient room. ICU patients were screened for VPPA on admission, at discharge, and weekly during hospitalization. GIS patients were screened for VPPA only on clinical indication. In this study, patient and sink isolates were typed at 8 loci using multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA). Results: Overall, 19 sink isolates from the ICU room were included. In 2013, VPPA isolates with identical VNTR genotypes (“clone B,” VNTR nos. 2-4-8-4-4-5-10-[-2]) were found in the wash basin, aerator, drain, and siphon. The drain plug was replaced in August 2013, but B was isolated from the drain 1 month later. Every year between 2014 and 2018, clone B and other closely related genotypes were recovered from this drain. In 2018, clone B was also found on the wash basin and counter. No positive patients were identified in this room until 2016, when a patient acquired clone B 6 days after admission. From the GIS room, 6 sink isolates and 4 patients’ isolates were included. In 2012, clone B was found on the wash basin and sink drain plug. Also, 3 VPPA-positive patients stayed in this room in 2012: at discharge, 1 patient was colonized by “clone A,” VNTR numbers 6-7-8-5-9-8-6-1. Furthermore, 2 other patients screened positive for clone B prior to admission in 2012, so they likely acquired VPPA elsewhere. The drain plug was replaced in 2013, and no VPPA was found again until 2017, when 2 VPPA-positive patients stayed in this room: 1 was already a carrier of clone B, and the other was a carrier of clone B 1 day after admission. No positive sink cultures were found until January 2018, when closely related B isolates were recovered from the wash basin, drain, and drain plug. Conclusions: Between 2013 and 2018, clone B persisted in the ICU room sink. In the GIS room sink, clone B may have disappeared after 2012, but it was reintroduced by known carriers. However, few patients became colonized after being admitted to these rooms, even when VPPA were discovered on surfaces outside the sink drain (ie, the wash basin and counter).

Funding: None

Disclosures: None