Molecular Epidemiology and Drug Resistance Pattern of Carbapenem-ResistantKlebsiella pneumoniaeIsolates from Iran

The emergence and dissemination of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates and their involvement in several nosocomial outbreaks are of high concern. This study was conducted to investigate the genetic relatedness and molecular determinants of carbapenem resistance in 100 CRKP isolates. Susceptibility to carbapenems as well as other antibiotics was determined by using disk diffusion method. The Modified Hodge test was performed for detection of carbapenemase production. The minimum inhibitory concentrations of selected antibiotics were determined by broth microdilution method. The presence of bla_OXA-48, bla_KPC, bla_NDM, and bla_VIM carbapenemase genes was examined by PCR, and clonal relatedness of CRKP isolates was investigated by pulsed-field gel electrophoresis (PFGE) analysis. bla_OXA-48 was the most frequent carbapenemase gene (72%), followed by bla_NDM (31%). None of the isolates harbored bla_KPC and bla_VIM genes. PFGE separated the majority of isolates into 10 clusters, including the major clusters A and B, carrying bla_OXA-48, and clusters C and D, carrying bla_NDM, and 4 isolates had a unique PFGE pattern. An increased rate of colistin resistance (50%) was detected among the isolates. Tigecycline was found to be the most active agent against CRKP isolates. Our results revealed that high prevalence of bla_OXA-48 and bla_NDM carbapenamses and resistance to colistin are alarming threats, necessitating an immediate action to prevent the spread of carbapenem-colistin-resistant K. pneumoniae isolates in Iran.