Molecular Characterization of Carbapenem-Resistant Klebsiella pneumoniae Species Isolated From a Tertiary Hospital, Ankara, Turkey

Carbapenem-resistant Klebsiella pneumoniae isolates can spread among the hospitalized patients and result in serious infections and increase mortality. Molecular studies provide useful information about resistance mechanisms and cross-transmission among the resistant isolates.
The current study aimed at investigating phenotypic and molecular characteristics of the carbapenem resistance and clonal relationship among the K. pneumoniae isolates recovered from infection sites and rectal swabs of the patients hospitalized in a tertiary hospital.
Resistance to carbapenems was investigated by disc-diffusion and E-test methods. Modified Hodge test (MHT) and ethylenediaminetetraacetic acid (EDTA)-combine disc (ECD) methods were performed to determine carbapenemases. Carbapenemase-encoding genes including blaOXA-48, blaNDM-1, blaKPC, blaIMP, and blaVIM were investigated by multiplex polymerase chain reaction (PCR). Clonal relationship among the isolates was determined by the pulsed-field gel electrophoresis (PFGE).
Carbapenem resistance was observed in 93 (5.8%) of the 1605 K. pneumoniae isolates. Majority (n = 66, 71%) of the resistant isolates were recovered from the patients in intensive care units (ICUs). Almost all carbapenem-resistant K. pneumoniae isolates (n = 91, 97.8%) were positive with MHT. Only 6 (6.5%) of the resistant isolates were positive with ECD method. The blaOXA-48 and blaNDM-1 were found in 90.3% (n = 84) and 6.5% (n = 6) of the resistant isolates, respectively. The pulsed-field gel electrophoresis yielded 55 different pulsotypes. Fifteen pulsotypes were identified as clusters with ≥ 2 isolates and a clustering rate of 57%. Based on the similarity coefficient higher than 85%, a total of 75 (80.6%) isolates were clonally related to each other.
The high rate of carbapenem resistance and 80.6% clonal relationship between the isolates collected in a 3-year period indicated a serious potential threat for the hospital-acquired infections and pointed longtime cross-contamination.