Plasmid-Related Resistance to Cefoxitin in Species of the Bacteroides fragilis Group Isolated from Intestinal Tracts of Calves
- 85 Downloads
Species of the Bacteroides fragilis group are considered the most common anaerobe in human and animal infections and also harbor plasmids conferring resistance to several antibiotics. In this study, resistance to cefoxitin, plasmid profile and β-lactamase production in species of the B. fragilis group isolated from intestinal tracts of calves were evaluated. One hundred sixty-one B. fragilis group bacteria isolated from calves with and without diarrhea were analyzed. Cefoxitin susceptibility was performed using an agar dilution method, β-lactamase production by using a nitrocefin method, and plasmid extraction by using a commercial kit. Minimal inhibitory concentration values for cefoxitin ranged from 32 to > 512 μg/ml, and 47 bacteria (29.2%) were resistant to cefoxitin (breakpoint 16 μl). Only seven isolates harbored plasmids varying from 6.0 to 5.0 kb, and a 5.5-kb plasmid in B. vulgatus Bd26e and B. fragilis Bc5j might be related to cefoxitin resistance. β-lactamase was detected in 33 (70.2%) isolates. The cepA gene was observed in total DNA and in the 5.5-kb plasmid. The plasmid presence in organisms isolated from cattle may be important in ecologic terms, and it needs further study.
KeywordsCefoxitin Brain Heart Infusion Agar Dilution Method Plasmid Profile Nitrocefin
This study was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP Grant Nos. 01/14139-3 and 02/02680-4).
- 1.Finegold SM, George WL (1989) Anaerobic infections in humans. San Diego, CA: Academic PressGoogle Scholar
- 13.National Committee for Clinical Laboratory Standards (1997) Methods for dilution antimicrobial susceptibility testing of anaerobic bacteria, 4th ed. Approved Standard M11-4. Villanova, PA: NCCLSGoogle Scholar