Clinical Microbiology and Antimicrobial Chemotherapy. 2017; 19(3):235-242
To assess an incidence rate of carbapenemase-producing Gram-negative bacteria isolated from patients in the RRCRST.
The clinical Gram-negative isolates obtained from patients hospitalized to the RRCRST over the period of February 2014 to April 2016 were tested. A screening for carbapenem resistance was performed by culture on chromogenic media, and species identification was made using MALDI-TOF massspectrometry. Susceptibility of Gram-negative bacteria to antimicrobial agents was determined using VITEK-2. Susceptibility testing results were interpreted according to EUCAST criteria v6.0 (2016). The genes encoding carbapenemases КРС, ОХА-48⁄162, VIM, IMP, NDM, OXA-51, OXA40/24, OXA-23 and OXA-58 were detected using real-time multiplex PCR.
A total of 813 Gram-negative bacteria isolates was obtained from 602 patients over the period of February 2014 to April 2016; of which 2.6% (21 isolates from 16 patients) were non-susceptible to meropenem and/or imipenem: Klebsiella pneumoniae (n=5), Enterobacter cloacae (n=2), Serratia marcescens (n=1), Pseudomonas aeruginosa (n=3), Acinetobacter baumannii (n=10). Up to 3 isolates of different carbapenem non-susceptible species was obtained from clinical specimens from the 4 patients. The genes encoding carbapenemases were detected in a total of 84% carbapenem non-susceptible isolates: A. baumannii – OXA40/24 (n=8); K. pneumoniae – OXA-48 (n=1), КРС (n=1) and NDM (n=2); P. aeruginosa – VIM (n=1) and KPC (n=1); E. cloacae – КРС (n=1). The OXA-48 carbapenemase was also detected in the one carbapenem-susceptible K. pneumoniae isolate. All of the tested carbapenemase-producing isolates were multidrug resistant (MDR).
Over the study period, a total of 21 carbapenem non-susceptible and multidrug resistant Gramnegative isolates were obtained. Most of these isolates carried genes encoding acquired carbapenemases. No one carbapenemase type was predominant in the carbapenemase-producing K. pneumoniae, E. cloacae and P. aeruginosa strains tested; however, all of the tested A. baumannii isolates carried the gene encoding OXA40/24 carbapenemase.