S Sageerabanoo1, A Malini2, T Mangaiyarkarasi3, G Hemalatha4
1Department of Microbiology, Dhanalakshmi Srinivasan Medical College, Perambalur, Tamil Nadu, India.
2Department of Microbiology, Indira Gandhi Medical College and Research Institute (Government of Puducherry Institute), Puducherry, India.
3Department of Microbiology, Sri Manakula Vinayagar Medical College, Puducherry, India.
4Department of Microbiology, Aarupadai Veedu Medical College, Puducherry, India.
Background: Production of β-lactamase enzymes by Gram-negative bacteria is the most common mechanism to acquire drug resistance to β-lactam antibiotics. Limitations in detecting extended spectrum β-lactamases (ESBL) and Amp-C β-lactamases have contributed to the uncontrolled spread of bacterial resistance and are of significant clinical concern. Materials and Methods: A total of 148 samples was selected on the basis of resistance against third-generation cephalosporin for screening ESBLs and Amp-C β-lactamases production. These multidrug-resistant strains were phenotypically screened for ESBL production by phenotypic confirmatory disc diffusion test and double disc synergy test. Modified three-dimensional method was used for Amp-C β-lactamases detection. Result: Among the 148 isolates, 82 (55.40%) were ESBL producers, and 115 (77.70%) were Amp-C β-lactamases producers. Co-existence of ESBL and Amp-C was observed in 70 (47.29%) isolates. Escherichia coli was the most common ESBL and Amp-C β-lactamase producer. All ESBL producers were highly resistant to ciprofloxacin (83.10%), cotrimoxazole (95.27%), and gentamicin (89.18%). However, these bacterial strains were sensitive to imipenem 146 (98.64%) and piperacillin/tazobactam 143 (96.62%). Conclusion: Our study showed that ESBL producing organisms were not only resistant to cephalosporins but also to other group of drugs and also that multiple mechanisms play a role in drug resistance among Gram-negative bacteria.
Keywords: Amp-C β-lactamase, extended spectrum β-lactamase, Gram-negative bacteria, minimum inhibitory concentration, multidrug resistance.