K. pneumoniae ssp pneumoniae is notorious for causing nosocomial as well as community-acquired infections. Over the decades, K. pneumoniae strains have increasingly acquired resistance to a wide range of antibiotics, one of the major mechanisms of resistance being expression of β-lactamases. Carbapenems have been the drug of choice for ESBL and Amp-C β-lactamase producing strains. The presence of carbapenemases like Metallo-β-lactamase renders the bacteria recalcitrant to treatment due to its broad-spectrum resistance profile. The MBL-positive strains are usually resistant to β-lactams, aminoglycosides and fluoroquinolones, leaving the treatment option with potentially toxic drugs like colistin. In the present study, 291 K. pneumoniae ssp pneumoniae clinical isolates were tested by Combined Disc Test for phenotypic detection of MBL production. A ≥ 7 mm increase in the inhibition zone diameter around imipenem+EDTA disk in comparison to imipenem-only disk was interpreted as a positive result for MBL production. Out of 191 MBL screen-positive isolates, 68 were confirmed to be MBL producers by CDT (23.37% prevalence of MBL producing isolates). MBL producing isolates were 98.5% resistant to amoxicillin-clavulanate combination,100% resistant to third-generation and fourth-generation cephalosporins, 100% resistant to carbapenems, 100% resistant to fluoroquinolone, 98.5% resistant to monobactams, 83-88% resistant to aminoglycosides and 75% resistant to cotrimoxazole. Maximum sensitivity was towards tigecycline (47.06%). This situation warrants a consistent surveillance of antimicrobial resistance of Klebsiella pneumoniae ssp pneumoniae and requires implementation of an efficient infection control programme.
Keywords: Klebsiella pneumoniae, Metallo-β-lactamase, antimicrobial susceptibility testing, Combined disc test, multi-drug resistant.

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Ved Prakash Mamoria

Professor and Head, Department of Microbiology, Mahatma Gandhi Medical College& Hospital, Jaipur (Raj.)