Phenotypic detection of ampc β-lactamase in clinical isolates of klebsiella spp. by an inhibitor based method using boronic acid

Klebsiella spp. are commonly encountered bacterial pathogens. β-lactamases produced in Klebsiella spp are mainly AmpC and Extended spectrum β-lactamases (ESBLs). ESBLs, confer resistance to penicillins, cephalosporins and monobactams but are inhibited by clavulanic acid. AmpC β-lactamases confer resistance to oximino cephalosporins, alpha methoxy beta lactams and monobactams. In the present study, a total of 100 isolates of Klebsiella spp. from various clinical specimenswere processed in the Department of Microbiology, Bangalore Medical College and Research Institute, Bengaluru for detection of antibiogram pattern, ESBL and AmpC production. Antimicrobial susceptibility testing by Kirby-Bauer technique was done according to Clinical Laboratory Standards Institute (CLSI) 2012 recommendations and detection of ESBL production was performed by Phenotypic confirmatory method recommended by CLSI. AmpC production was initially screened using Cefoxitin resistance and later confirmed by the use of an inhibitor based method employing Boronic acid. 32 Klebsiella spp. isolates were found to be pure AmpC producers and 2 isolates were noted to have co-existence of ESBL and AmpC. The study revealed a high prevalence of AmpC producing Klebsiella spp. in our hospital, being most susceptible to Piperacillin - Tazobactam. A multidisciplinary approach to infection control with greater emphasis on detection of antimicrobial resistance among Gram negative bacteria accompanied by rational antimicrobial usage is needed to counter the infections of ESBL and AmpC producing pathogens.