Evaluation of phenotypic tests for the detection of AmpC beta-lactamase in clinical isolates of Escherichia coli.
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Date
2013-04
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Abstract
Background: AmpC beta lactamases are cephalosporinases that confer
resistance to a wide range of beta lactam drugs thereby causing serious
therapeautic problem. As there are no CLSI guidelines for detection of AmpC
mediated resistance in Gram negative clinical isolates and it may pose a
problem due to misleading results, especially so in phenotypic tests. Although
cefoxitin resistance is used as a screening test, it does not reliably indicate
AmpC production. Materials and Methods: We planned a study to determine
the occurrence of AmpC beta lactamase in hospital and community, clinical
isolates of Escherichia coli and simultaneously evaluate different phenotypic
methods for detection of AmpC beta lactamases. Results: It was observed that
82.76% isolates were ESBL positive and 59% were cefoxitin screen positive.
Using phenotypic confi rmatory tests the occurrence of Amp C beta lactamases
was found to be 40% and 39% by inhibitor based method using boronic acid
(IBM) and modifi ed three dimensional test (M3D) respectively. Conclusion:
Both the test showed concordant result. Co-production was observed in
84.62% isolates Screening of ESBL and Amp C can be done in routine clinical
microbiology laboratory using aztreonam and IBM respectively as it is a simple,
rapid and technically less demanding procedure which can be used in all clinical
laboratories.
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Keywords
AmpC beta-lactamases, extended spectrum beta-lactamases, inhibitor based test, modifi ed 3D test
Citation
Handa Deepika,Pandey Anita, Asthana Ashish Kumar, Rawat Ashutosh, Handa Seemant, Thakuria Bhaskar. Evaluation of phenotypic tests for the detection of AmpC beta-lactamase in clinical isolates of Escherichia coli. Indian Journal of Pathology & Microbiology. 2013 Apr-Jun 56 (2): 135-138.