Extended-spectrum β-lactamase and carbapenemase production among burn and non-burn clinical isolates of Klebsiella pneumoniae

BACKGROUND AND OBJECTIVES: Klebsiella pneumoniae is an opportunistic pathogen responsible for up to 10% of nosocomial infections. The emergence and spread of multidrug resistant K. pneumoniae, mostly due to the production of extended-spectrum β-lactamases (ESBL) and carbapenemases, is often responsible for antibiotic treatment failure of these infections. We compared the antibiotic resistance profiles, ESBL and carbapenemase production as well as presence of KPC-type genes in burn and non-burn clinical isolates of K. pneumoniae. MATERIALS AND METHODS: Fifty five clinical isolates were collected from Shahid Motahari (25 burn isolates) and Shariati (30 non-burn isolates) hospitals between August 2011 to January 2012. Antibiotic susceptibility was determined to 12 antibiotics using disc diffusion. The phenotypic confirmatory test (PCT) was used to screen for ESBL production. Carbapenemase activity was measured by the modified Hodge test (MHT) and KPC-type carbapenemases were further sought by PCR using specific primers. RESULTS: Both groups were highly resistant to cefotaxime and ceftazidime (>92%). Burn isolates were significantly more resistant to cefepime, amoxiclav, imipenem, meropenem, gentamicin and ciprofloxacin compared to the non-burn strains (p<0.05). No significant differences were observed in ESBL production between the two groups. Carbapenem resistance was only observed among the burn isolates (n=5, 9.1%). Five carbapenem-resistant isolates produced carbapenemases. However, none of the isolates harbored the KPC-type genes. CONCLUSION: Higher rates of drug resistance were observed in burn isolates of K. pneumoniae compared to the non-burn strains. Carbapenemase phenotype was only observed among the burn isolates but KPC-type gene was not detected.