DETECTION OF KLEBSIELLA PNEUMONIAE CARBAPENEMASES AMONG GRAM NEGATIVE CLINICAL ISOLATES

Abstract

Carbapenem-resistant Gram negative bacteria have recently evolved as a significant problem in the health care. One of the mechanisms of resistance to carbapenems is related to their ability to produce Klebsiella pneumoniae Carbapenemase (KPC) enzymes. This study aimed to evaluate carbapenem resistance in Gram negative clinical isolates with particular emphasis on KPC detection as the probable mechanism of resistance among these isolates. Out of 120 different clinical samples 66 Gram negative bacilli were isolated, identified, and subjected to antimicrobial susceptibility testing by disk diffusion test against three carbapenem antibiotics (Imipenem, Ertapenem, and Meropenem). Isolates resistant to any of the tested carbapenems were further screened for carbapenemase by the modified Hodge test (MHT). KPC production was tested for by phenyl boronic acid - combined disk (PBA-CD) test and detection of blaKPC gene by polymerase chain reaction (PCR).Totally, out of the 66 Gram negative isolates, 23 (34.8%) showed resistance to carbapenems. The carbapenem resistant Gram negative bacilli were; Acinetobacter baumanni (5/11; 45.5%), Pseudomonas aeruginosa (8/21; 38.1%), and Enterobacteriacae (10/34; 29.4%). Resistance to carbapenems among Enterobacteriacae was detected in 7 isolates of Klebsiella pneumoniae (20.6%) and 3 isolates of Proteus mirabilis (8.8%). Among the carbapenem resistant isolates the blaKPC gene was detected in 6 isolates (26.1%); all were Klebsiella pneumoniae (6/7; 85.7%). The MHT detected 4 out of 6 blaKPC producing isolates; meanwhile, the PBA-CD test detected all blaKPC producing isolates. The blaKPC gene was not detected in carbapenem resistant isolates of either Pseudomonas aeruginosa or Acinetobacter baumanni. The agreement between blaKPC PCR and the PBA-CD test and MHT was 82.6% and 73.9% respectively. In conclusion, KPC production is an important mechanism of carbapenem resistance among Enterobacteriacae. Rapid identification of KPC would be a key to limit the spread of such resistant strains. PBA-CD test can be a simple rapid screening test for detecting KPC mediated carbapenem resistance.