Phenotypic detection of extended spectrum β-lactamase and Amp-C β-lactamase producing clinical isolates in a Tertiary Care Hospital: A preliminary study.
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.


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.


RESULTS
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%).


CONCLUSIONS
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.
Department of Microbiology, Dhanalakshmi Srinivasan Medical College, Perambalur, Tamil Nadu, India.
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Sageerabanoo
Department of Microbiology, Indira Gandhi Medical College and Research Institute (Government of Puducherry Institute), Puducherry, India.
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Malini
Department of Microbiology, Sri Manakula Vinayagar Medical College, Puducherry, India.
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Mangaiyarkarasi
Department of Microbiology, Aarupadai Veedu Medical College, Puducherry, India.
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Hemalatha
Amp-C β–lactamase; Gram-negative bacteria; extended spectrum β-lactamase; minimum inhibitory concentration; multidrug resistance