Co-occurrence of VIM-positive non-aeruginosa Pseudomonasspp. andPseudomonas aeruginosain the hospital: A detailed molecular comparison ofbla_VIM-2-containing plasmids from environmental and clinical isolates

Abstract

BackgroundPseudomonas aeruginosais a bacterial pathogen responsible for severe hospital-acquired infections, and is capable of forming persistent reservoirs in hospital sink drains, creating a transmission risk. In our hospital, we have cultured not only carbapenemase-producing, Verona Integron-encoded Metallo-beta-lactamase (VIM)-positiveP. aeruginosa, but also VIM-positive non-aeruginosa Pseudomonasspp., from sink drains. Previously, ablaVIM-2-containing, conjugative plasmid conferring carbapenem resistance was found in a clinicalP. aeruginosaisolate in our hospital.ObjectiveTo investigate if otherPseudomonasspp. from our hospital also carried ablaVIM-2-containing plasmid, genetically characterize these plasmids, and compare these plasmids to publicly-available plasmid sequences to identify their source.MethodsWhole-genome sequencing was used to sequence chromosomes and possible plasmids from VIM-positive non-aeruginosa Pseudomonasspp. and VIM-positiveP. aeruginosastrains. Hybrid assemblies were generated to reconstruct plasmid sequences. All isolates were obtained from environmental sampling or clinical cultures during a prolonged VIM-positiveP. aeruginosaoutbreak in our hospital.ResultsAn identicalblaVIM-2-containing plasmid was found in six non-aeruginosa Pseudomonas(P. carnis,P. oleovorans, and a novel species) and in threeP. aeruginosaisolates. The previously-reportedblaVIM-2-containing plasmid was found in three additionalP. aeruginosaisolates. AllP. aeruginosabelonged to high-risk clones ST111 or ST446. The two plasmids were derived from both clinical isolates and isolates from sink cultures, and were unique to our hospital when compared to other publicly-available plasmid sequences.ConclusionsDuring a VIM-positiveP. aeruginosaoutbreak in our hospital, two closely-related,blaVIM-2-containing plasmids co-occurred in multiple non-aeruginosa Pseudomonasspp. and in high-riskP. aeruginosaclones ST111 and ST446. Non-aeruginosa Pseudomonasspp. cultured from either patient or sink samples may be important sources of carbapenem resistance genes, and should not be overlooked during outbreak investigations. Moreover, plasmid analysis is essential to fully understand transmission routes in hospitals.