A Comparative Study between Different Laboratory Tests for Detection of Carbapenem Resistance in Klebsiella Pneumoniae

Abstract

Background : Klebsiella pneumoniae is among the most common gram-negative bacteria encountered by physicians worldwide. It is a common hospital-acquired pathogen, causing urinary tract infections, nosocomial pneumonia, and intra abdominal infections. K. pneumoniae is also a potential community-acquired pathogen. Objectives : were to determine carbapenem resistance among Klebsiella pneumonia isolates by routine disc diffusion test and E test, determine carbapenemase production by modified Hodge test and to study the presence of bla KPC gene in carbapenem-resistant and carbapenem sensitive Klebsiella pneumoniae isolates. Methodology : Fifty klebsiella pnumoniae isolates were identified and subjected to antimicrobial susceptibility testing by disk diffusion test against three carbapenem antibiotics (Imipenem, Ertapenem, and Meropenem) and were subjected to determination of minimum inhibitory concentration (MIC) to ertapenem using E-test. Modified Hodge test was carried out for strains included in the study. Twenty-six K. pneumoniae isolates were subjected to PCR for detection of bla kpc gene. Thirteen confirmed carbapenem resistant isolates by disc diffusion, E-test and MHT and 13 confirmed carbapenem sensitive isolates by the same tests. Results: 13/50 (26%) isolates were resistant to both meropenem and ertapenem while only 11/50(22%) isolates were resistant to imipenem. Ertapenem sensitivity tests revealed that there was a discrepancy between the results of E test and disc diffusion method in two strains. The two strains were reported resistant by disc diffusion method and intermediate sensitive by E test. All carbapenem resistant strains 13 out of 50 strains showed positive modified Hodge test. The 26 isolates tested for bla kpc gene were negative. In conclusion resistance of K.pneumoniae to carbapenems was detected in 26% of isolates . The disc diffusion susceptibility did not report major errors in comparison to E test for ertapenem. Expression of carbapenemase was detected in all carbapenem resistant isolates by modified Hodge test while bla KPC gene was not detected among either carbapenem resistant or susceptible strains.