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Res Microbiol. 2004 Dec;155(10):843-6.

Plasmid-related beta-lactamase production in Bacteroides fragilis strains.

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Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, Av. Prof. Lineu Prestes 1374, São Paulo, 05508-900 SP, Brazil.


Twenty Bacteroides fragilis group species isolated from children with and without diarrhea were analyzed. Antibiotic susceptibility was performed using an agar dilution method; beta-lactamase production was determined using a nitrocefin method, and plasmids were extracted using a commercial Miniprep System. MIC values ranged from 16 to 256 microg/ml for penicillin, 4-128 microg/ml for amoxicillin/clavulanic acid, 0.25-256 microg/ml for clindamycin, and 16-256 microg/ml for penicillin. beta-Lactamase was detected in all isolates. Only five isolates harbored plasmids varying from 7.8 to 1.8 kb. Loss of 6.4- and 3.8-kb plasmids in B. fragilis C68c was related to antibiotic resistance. Low molecular weight plasmids of 2.8-1.8 kb were stable. PCR amplification of cfiA and cepA genes was observed using total DNA, and the cfiA gene was also amplified from the 6.4-kb plasmid.

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