beta-lactamases in Shigella flexneri isolates from Hong Kong and Shanghai and a novel OXA-1-like beta-lactamase, OXA-30.
Ninety-one ampicillin-resistant Shigella flexneri strains from Hong Kong and Shanghai were studied for production of beta-lactamases. TEM-1-like and OXA-1-like enzymes were identified in 21 and 79% of the strains, respectively, by isoelectric focusing (IEF). No difference in the pattern of beta-lactamase production was found between strains from Hong Kong and Shanghai. Four ribotypes were detected. Over 88% of OXA-producing strains had the same ribotype. All TEM-1-like strains harbored a plasmid which hybridized positively with the bla(TEM) probe. Total DNA from OXA-1-like strains failed to hybridize or only hybridized weakly with an OXA probe. The OXA resistance was not transferable. OXA-1-like enzymes exhibited substrate and inhibition profiles similar to that of OXA-1 and were shown to have a pI of 7.3 by further IEF using a narrow-range ampholine gel. The gene encoding the OXA-1-like enzyme from one isolate (CH-07) was cloned, sequenced, and found to differ from bla(OXA-1) at codon 131 (AGA-->GGA; Arg to Gly), resulting in the novel designation OXA-30. The predominance of OXA-type enzymes in ampicillin-resistant S. flexneri suggests host preference for specific beta-lactamases.[1]References
- beta-lactamases in Shigella flexneri isolates from Hong Kong and Shanghai and a novel OXA-1-like beta-lactamase, OXA-30. Siu, L.K., Lo, J.Y., Yuen, K.Y., Chau, P.Y., Ng, M.H., Ho, P.L. Antimicrob. Agents Chemother. (2000) [Pubmed]
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