Transmission of VIM-producing Enterobacteriaceae over a two-year period linked to contaminated drains

Background: Over a 2-year period, among 8 patients colonized or infected with carbapenamase-producing Enterobacteriaceae (CPE), we identified 6 patients with VIM-producing Enterobacter spp. We describe the outbreak investigation that led to examination of hospital drains as the potential source.

Methods: Outbreak investigation involved a retrospective chart review to identify potential epidemiological links. Patient rectal swabs, clinical specimens and environmental specimens, which included tap water, and swabs of faucets, sinks and shower drains, were screened for CPE. Carbapenamase genes were tested by multiplex PCR and alleles confirmed by Sanger sequencing. Clonality was evaluated using pulse-field gel electrophoresis (PFGE) with restriction enzyme XbaI and BlnI.

Results: Over a 2-year period, 4 patients (including one identified at a different hospital) with previous admission to a general medicine unit in our hospital were found to be colonized with a VIM-producing Enterobacter spp. An additional two patients had pseudo-infections with the same VIM-producing clone. Retrospective epidemiological review revealed all six patients had the same environmental exposure to one of two different rooms on the unit. VIM-producing Enterobacter spp. isolates were identified from environmental samples taken from hand hygiene sink drains and shower drains of both rooms. PFGE revealed genetic relatedness and the presence of bla_VIM-1 gene was confirmed in all isolates from patients and environmental specimens. To stop the spread of CPE, both rooms were closed to patients, and sink drains and their hardware were replaced. Shower drains were chemically disinfected and steamed. All follow up environmental screening swabs have since been negative for CPE. Post-room closure and remediation, active screening of unit patients and environmental contacts has not identified additional cases.

Conclusion: Contaminated drains in patient rooms are emerging as reservoirs of CPE in hospitals, and should be considered during outbreak investigations.