Approach to Carbapenemase Detection in Klebsiella pneumoniae in Routine Diagnostic Laboratories

Abstract

Introduction: Resistance to Carbapenems in Klebsiella may be due to Carbapenem hydrolysing enzymes. Accurate detection of carbapenemase must be done for patient treatment and epidemiological purposes. Aim: To detect carbapenemase production by performing Modified Hodge Test (MHT), Combined Disk Test (CDT) for Metallo-b-Lactamases (MBL) and PCR for blaKPC gene, to evaluate the performance of MHT using MacConkey Agar (MCA) and to access the value of MHT for carbapenemase detection. Material and Methods: Using a prospective laboratory study design, 153 Extended Spectrum Beta-Lactamases (ESBL) producing Klebsiella pneumoniae from clinical samples of patients admitted in the Kasturba Medical College were collected from January 2014 to December 2015. Isolates resistant to carbapenems by disk diffusion were subjected to MHT on MCA and Mueller Hinton agar (MHA). All isolates were tested for (MBL) production by Imipenem and Imipenem-EDTA CDT and subjected to PCR for the presence of blaKPC gene. Results: Out of 153 isolates, 54 were resistant to one of the carbapenems. Among these, 13 were positive for MHT on MHA, while 23 were positive by MHT on MCA. Number of MBL producers was 23 (42.5%), while blaKPC was detected in 2 out of the 54 isolates. Conclusion: Though detection of drug resistance gene remains the method of choice, it can be performed only in centers with adequate resources. Hence, for most laboratories in resource poor countries, the MHT performed on MCA with concomitant CDT for MBL detection seem to be a better option for detection of Carbapenem resistance.

Keywords

• carbapenems
• extended spectrum beta-lactamases
• metallo-β-lactamase
• modified hodge test