Molecular Characterization of Pseudomonas putida Group Isolates Carrying bla_VIM-2 Disseminated in a University Hospital in Korea

Pseudomonas putida group are Gram-negative bacilli with polar flagellation, which are ubiquitous in the environment, although they are rarely involved in human infections. The aim of this study was to identify the dissemination of VIM-2-producing P. putida group in clinical isolates from a hospital in Korea. Thirteen strains were collected from 2014 to 2015 for the study. The isolates were recovered from urine cultures of both inpatients and outpatients at the hospital. Minimum inhibitory concentrations of antibiotics were determined by Etest. Carbapenemase genes were amplified by polymerase chain reaction and sequenced. Pulsed-field gel electrophoresis was performed for strain typing. Whole-genome sequencing was carried out randomly for two strains chosen from each year of the study to analyze the plasmid structure carrying the bla_VIM-2 genes. The 13 isolates carried nine different class I integrons harboring VIM-2 and were resistant to meropenem and imipenem (minimum inhibitory concentrations, ≥32 μg/ml), thus exhibiting a multidrug-resistant phenotype. The bla_VIM-2 gene was located on a plasmid in seven of the isolates and on the chromosome in six isolates. Each case of the bla_VIM-2 gene was disseminated by clonal spread, horizontal transfer, and was mostly an occasional occurrence. In this study, we demonstrated that multidrug-resistant P. putida group carrying VIM-2 has reemerged in human specimens in Korea.