Prevalence and genetic analysis of multidrug-resistant Pseudomonas aeruginosa ST235 isolated from a hospital in Korea, 2008-2012.

Pseudomonas aeruginosa is one of the primary opportunistic pathogens responsible for nosocomial infections. Recently, sequence type 235 (ST235) has been found internationally in a multidrug-resistant clone and is involved in the dissemination of genes encoding IMP-6 and VIM-2. This study aimed to describe the prevalence of metallo-β-lactamase (MBL), epidemiological relationship, and genetic characterization to aminoglycoside resistance in carbapenem-resistant P. aeruginosa isolates obtained from a tertiary hospital in Daejeon, Korea, from 2008 to 2012. Minimum inhibitory concentrations (MICs) of six antimicrobial agents were determined using the agar dilution method. PCR and DNA sequencing were used to identify MBL genes, class 1 integrons, and genes contributing to the aminoglycoside resistance phenotype. In addition, an epidemiological relationship was investigated by multilocus sequence typing (MLST). Eleven (16.2%) carbapenem-resistant isolates were MBL-producers; the major MBL type was IMP-6 (10 isolates). IMP-6-producing isolates were multidrug-resistant and belonged to ST235. All IMP-6-producing isolates had class 1 integrons (5.5 Kb; blaIMP-6-qac-aacA4-blaOXA-1-addA1). We identified genetic characteristics in aminoglycoside genes between ST235 and non-ST235. All ST235 isolates contained aminoglycoside-modifying enzyme (AME) genes, whereas 23.5% of non-ST235 isolates contained AME genes. Development and spread of the aminoglycoside resistance gene in P. aeruginosa non-ST235 could result in multidrug resistance in the future.