Identification of Klebsiella pneumoniae Carbapenemase-producing Klebsiella oxytoca in Clinical Isolates in Tehran Hospitals, Iran by Chromogenic Medium and Molecular Methods

OBJECTIVES Production of carbapenemase, especially Klebsiella pneumoniae carbapenemases (KPC), is one of the antibiotic resistance mechanisms of Enterobacteriaceae such as Klebsiella oxytoca. This study aimed to investigate and identify KPC-producing K. oxytoca isolates using molecular and phenotypic methods. METHODS A total of 75 isolates of K. oxytoca were isolated from various clinical samples, and were verified as K. oxytoca after performing standard microbiological tests and using a polymerase chain reaction (PCR) method. An antibiotic susceptibility test was performed using a disc diffusion method according to the Clinical and Laboratory Standards Institute guidelines. CHROMagar KPC chromogenic culture media was used to examine and confirm the production of the carbapenemase enzyme in K. oxytoca isolates; in addition, PCR was used to evaluate the presence of blaKPC gene in K. oxytoca strains. RESULTS Of a total of 75 K. oxytoca isolates, one multidrug resistant strain was isolated from the urine of a hospitalized woman. This strain was examined to assess its ability to produce carbapenemase enzyme; it produced a colony with a blue metallic color on the CHROMagar KPC chromogenic culture media. In addition, the blaKPC gene was confirmed by PCR. After sequencing, it was confirmed and deposited in GenBank. CONCLUSION To date, many cases of KPC-producing Enterobacteriaceae, in particular K. pneumoniae, have been reported in different countries; there are also some reports on the identification of KPC-producing K. oxytoca. Therefore, to prevent the outbreak of nosocomial infections, the early detection, control, and prevention of the spread of these strains are of great importance.