The role of the blaKPC gene in antimicrobial resistance of Klebsiella pneumoniae

Klebsiella pneumoniae isolates that produce K. pneumoniae carbapenemase (KPC) have become a grave concern for the treatment of infections. KPC-producing strains are not only able to hydrolyze carbapenems but are also resistant to a variety of β-lactam and non-β-lactam antibiotics. The present study evaluated the prevalence of blaKPC in K. pneumoniae infections and determined the antimicrobial susceptibility of the isolates.

The K. pneumoniae isolates were identified by biochemical tests and confirmed by genotyping. The modified Hodge test (MHT) was performed to detect carbapenemases, and antimicrobial susceptibility was determined for all isolates by the disc diffusion method. Also, for MHT-positive isolates, supposed to carbapenemases isolates, broth microdilution method was used to measure the minimum inhibitory concentrations (MICs) of meropenem and colistin.

The blaKPC genotypic evaluation revealed that only 5 of 96 isolates carried blaKPC genes. Antimicrobial pattern showed that isolates carrying blaKPC were resistant to cefepime, ticarcillin/tazobactam, and aztreonam discs. Also, results of broth microdilution method showed that KPC-producing K. pneumoniae was resistant to meropenem and colistin, according to the CLSI and EUCAST.

In this study nearly half the isolates showed carbapenemase activity as shown by MHT results, but only few of them were carrying blaKPC. Thus blaKPC gene is not the main cause of resistance spread to carbapenems in Isfahan, Iran.