Detection and assay of beta-lactamases in clinical and non-clinical strains of Yersinia enterocolitica biovar 1A.
OBJECTIVE
To detect beta-lactamases (A & B) and extended-spectrum beta-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 beta-lactamases and ESBLs was detected by disc diffusion in 219 (36 clinical, 183 non-clinical) isolates. beta-Lactamase activity was assayed spectrophotometrically in all 36 clinical and 10 representative non-clinical isolates using nitrocefin as the substrate. Inhibition of beta-lactamases was studied by clavulanic acid, aztreonam and cloxacillin.


RESULTS
Of the 219 isolates, all except two non-clinical isolates indicated the presence of beta-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. beta-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.


CONCLUSIONS
This is the first report on beta-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.
Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi-110 021, India.
Sachin
S
Sharma
Priya
P
Ramnani
J S
JS
Virdi
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005399:Fishes; D006801:Humans; D007194:India; D008826:Microbial Sensitivity Tests; D013552:Swine; D015009:Yersinia Infections / Q000382:microbiology*; D015008:Yersinia enterocolitica / Q000187:drug effects / Q000201:enzymology*; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000032:analysis* / Q000096:biosynthesis
D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases