Similar frequencies of Pseudomonas aeruginosa isolates producing KPC and VIM carbapenemases in diverse genetic clones at tertiary-care hospitals in Medellín, Colombia

Abstract

Carbapenem-resistant Pseudomonas aeruginosa has become a serious health threat worldwide due to the limited options available for its treatment. Understanding its epidemiology contributes to the control of antibiotic resistance. The aim of this study was to describe the clinical and molecular characteristics of infections caused by carbapenem-resistant P. aeruginosa isolates in five tertiary-care hospitals in Medellín, Colombia. A cross-sectional study was conducted in five tertiary-care hospitals from June 2012 to March 2014. All hospitalized patients infected by carbapenem-resistant P. aeruginosa were included. Clinical information was obtained from medical records. Molecular analyses included PCR for detection of bla(VIM), bla(IMP), bla(NDM), bla(OXA-48), and bla(KPC) genes plus pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) for molecular typing. A total of 235 patients were enrolled: 91.1% of them were adults (n = 214), 88.1% (n = 207) had prior antibiotic use, and 14.9% (n = 35) had urinary tract infections. The bla(VIM-2) and bla(KPC-2) genes were detected in 13.6% (n = 32) and 11.5% (n = 27), respectively, of all isolates. Two isolates harbored both genes simultaneously. For KPC-producing isolates, PFGE revealed closely related strains within each hospital, and sequence types (STs) ST362 and ST235 and two new STs were found by MLST. With PFGE, VIM-producing isolates appeared highly diverse, and MLST revealed ST111 in four hospitals and five new STs. These results show that KPC-producing P. aeruginosa is currently disseminating rapidly and occurring at a frequency similar to that of VIM-producing P. aeruginosa isolates (approximately 1:1 ratio) in Medellín, Colombia. Diverse genetic backgrounds among resistant strains suggest an excessive antibiotic pressure resulting in the selection of resistant strains.

FIG 1

Rates of resistance among noncarbapenemase-producing and carbapenemase-producing P. aeruginosa isolates. (A) Percentages of isolates resistant to individual antibiotics. (B) Resistance profiles of carbapenem-resistant isolates. Mem, meropenem; Ipm, imipenem; Cip, ciprofloxacin; Amk, amikacin; Gen, gentamicin.

FIG 2

Genetic relatedness of KPC-producing P. aeruginosa isolates. The broken line corresponds to the cutoff level (80%) used to define PFGE clones as related. Boxes indicate the main clusters found at each hospital.

FIG 3

Genetic relatedness of VIM- and noncarbapenemase-producing P. aeruginosa isolates. The broken line corresponds to the cutoff level (80%) used to define PFGE clones as related. (A) VIM-producing isolates. (B) Noncarbapenemase-producing isolates.