Journal Article

Detection and assay of β-lactamases in clinical and non-clinical strains of <i>Yersinia enterocolitica</i> biovar 1A

Sachin Sharma, Priya Ramnani and J. S. Virdi

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 54, issue 2, pages 401-405
Published in print August 2004 | ISSN: 0305-7453
Published online August 2004 | e-ISSN: 1460-2091 | DOI:
Detection and assay of β-lactamases in clinical and non-clinical strains of Yersinia enterocolitica biovar 1A

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Objectives: To detect β-lactamases (A & B) and extended-spectrum β-lactamases (ESBLs) in clinical and non-clinical isolates of Yersinia enterocolitica biovar 1A, and to determine their activity in the presence of specific lactamase inhibitors.

Methods: The presence of β-lactamases and ESBLs was detected by disc diffusion in 219 (36 clinical, 183 non-clinical) isolates. β-Lactamase activity was assayed spectrophotometrically in all 36 clinical and 10 representative non-clinical isolates using nitrocefin as the substrate. Inhibition of β-lactamases was studied by clavulanic acid, aztreonam and cloxacillin.

Results: Of the 219 isolates, all except two non-clinical isolates indicated the presence of β-lactamase A (Bla-A) based on the smaller (2–8 mm) radius of the inhibition zone around the ticarcillin disc. Synergy between ticarcillin and co-amoxiclav discs was, however, observed in only 34% of isolates of non-clinical origin. β-Lactamase B (Bla-B) was found to be consistently positive among all the clinical and non-clinical isolates, as indicated by its characteristic appearance of flattening of the zone of inhibition around the cefotaxime disc adjacent to an imipenem disc. Bla-B was induced more strongly in clinical than in non-clinical isolates. Inhibition of enzyme A by clavulanic acid, aztreonam and cloxacillin was found to be similar, whereas enzyme B was inhibited more strongly by aztreonam and cloxacillin. None of the isolates showed the unequivocal presence of ESBL.

Conclusion: This is the first report on β-lactamases of Yersinia enterocolitica biovar 1A from Asia. Y. enterocolitica biovar 1A expressed both Bla-A and Bla-B. Heterogeneity was, however, discerned in the expression of Bla-A and by induction of Bla-B among clinical and non-clinical isolates of Y. enterocolitica biovar 1A.

Keywords: constitutive Bla-A; inducible Bla-B; nitrocefin; synergy

Journal Article.  2942 words. 

Subjects: Medical Oncology ; Critical Care

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