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International Journal of Recent Trends in Science and Technology, ISSN 2277-2812 E-ISSN: 2249-8109

Volume 9, Issue 3, January 2014 pp 358-360

Research Article

Detection of AmpC β-Lactamases among Gram Negative Clinical Isolates


Vijaya Shivanna1, Achut Rao2

1Assistant Professor, Department of Microbiology, Adichunchanagiri Institute of Medical Sciences

Balagangadhara natha Nagara,Mandya Dist, Karnataka, INDIA.

2Professor and Head, Dept. of Microbiology, Navodaya Medical College, Raichur, Karnataka, INDIA.

Academic Editor : Dr. Aher K. R.



Background and Objectives: AmpC β-lactamases confer resistance to a wide variety of β-lactam antibiotics including cephamycins such as cefoxitin and cefotetan, narrow and broad spectrum cephalosporins, aztreonam and are poorly inhibited by β-lactamase inhibitors such as clavulanic acid. The present study was undertaken to determine the occurrence of AmpC enzyme producing Gram negative clinical isolates at Navodaya Medical College, Raichur.Materials and Methods: 200 non-repeat Gram negative clinical isolates from various samples were screened for AmpC β- lactamases by using Modified disc Approximation method. The “Screen positive” isolates were detected for AmpC β-lactamase by Modified three-dimensional enzyme extract test, AmpC disk test, and phenyl boronic acid test.Results: Out of the 200 Gram negative isolates, 87 (43.5%) isolates were screened to be positive and 10 (5%) isolates were inducible AmpC producers. Of these 97 isolates subjected to confirmatory tests, 74 (37%) were harbouring AmpC enzymes. Majority of AmpC positive isolates were E.coli (20.5%), K.pneumoniae (5.5%) and Acinetobacter spp. (3.5%).Conclusion: Phenyl boronic acid test is the simple and practical method for the detection of AmpC in routine clinical microbiology laboratories. Plasmid-mediated AmpC β-lactamases have been associated with false in vitro susceptibility to cephalosporins. Thus, the type of β-lactamase produced by the organism should be detected along with the antibiogram for appropriate treatment of the patient.