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Antimicrobial Agents and Chemotherapy, August 2000, p. 2034-2038, Vol. 44, No. 8
Department of Microbiology, The University of
Hong Kong,1 and Department of
Health,2 Hong Kong, China
Received 8 October 1999/Returned for modification 5 April
2000/Accepted 11 May 2000
Ninety-one ampicillin-resistant Shigella flexneri
strains from Hong Kong and Shanghai were studied for
production of
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
-Lactamases in Shigella flexneri
Isolates from Hong Kong and Shanghai and a Novel OXA-1-Like
-Lactamase, OXA-30

-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
-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
blaTEM 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 blaOXA-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
-lactamases.
*
Corresponding author. Mailing address: Department of
Microbiology, The University of Hong Kong, Pokfulam Rd., Hong
Kong, China. Phone: (852) 28554892. Fax: (852) 28551241. E-mail:
plho{at}hkucc.hku.hk.
Present address: Clinical Research Division, National Health
Research Institute, Taipei, Taiwan, Republic of China.
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