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.
Siu
L K
LK
Department of Microbiology, The University of Hong Kong.
Lo
J Y
JY
Yuen
K Y
KY
Chau
P Y
PY
Ng
M H
MH
Ho
P L
PL
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015139:Blotting, Southern; D002681:China; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000032:analysis; D006723:Hong Kong; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D012763:Shigella flexneri / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D013379:Substrate Specificity; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D047090:beta-Lactams; C039404:beta-lactamase OXA-2; C413936:beta-lactamase OXA-30; D001618:beta-Lactamases