Co-occurrence of VIM-positive non-aeruginosa Pseudomonas spp. and Pseudomonas aeruginosa in the hospital: A detailed molecular comparison of blaVIM-2-containing plasmids from environmental and clinical isolates

Background Pseudomonas aeruginosa is 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)-positive P. aeruginosa , but also VIM-positive non- aeruginosa Pseudomonas spp., from sink drains. Previously, a bla VIM-2 -containing, conjugative plasmid conferring carbapenem resistance was found in a clinical P. aeruginosa isolate in our hospital. Objective To investigate if other Pseudomonas spp. from our hospital also carried a bla VIM-2 -containing plasmid, genetically characterize these plasmids, and compare these plasmids to publicly-available plasmid sequences to identify their source. Methods Whole-genome sequencing was used to sequence chromosomes and possible plasmids from VIM-positive non- aeruginosa Pseudomonas spp. and VIM-positive P. aeruginosa strains. Hybrid assemblies were generated to reconstruct plasmid sequences. All isolates were obtained from environmental sampling or clinical cultures during a prolonged VIM-positive P. aeruginosa outbreak in our hospital. Results An identical bla VIM-2 -containing plasmid was found in six non- aeruginosa Pseudomonas ( P. carnis , P. oleovorans , and a novel species) and in three P. aeruginosa isolates. The previously-reported bla VIM-2 -containing plasmid was found in three additional P. aeruginosa isolates. All P. aeruginosa belonged 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. Conclusions During a VIM-positive P. aeruginosa outbreak in our hospital, two closely-related, bla VIM-2 -containing plasmids co-occurred in multiple non- aeruginosa Pseudomonas spp. and in high-risk P. aeruginosa clones ST111 and ST446. Non- aeruginosa Pseudomonas spp. 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.