Resistance profile of Bacteroides fragilis isolated in Brazil. Do they shelter the cfiA gene?

The epidemiology of antimicrobial resistance of clinical isolates and human intestinal strains of Bacteroides fragilis has assumed great importance in the last few years since this microorganism, like other members of the B. fragilis group, can be responsible for the spread of resistance determinant s. It is possible that the presence of B. fragilis in polluted aquatic envi ronments might contribute to the spread of resistance. The antimicrobial re sistance profile of 44 clinical B. fragilis strains isolated from 1981-1988 and 1991-1998 from the University hospital of Rio de Janeiro, and of 17 fa ecal and 17 polluted aquatic environmental B. fragilis strains isolated bet ween 1991 and 1998 was determined. The susceptibility tests against penicil lin, cefoxitin, imipenem, meropenem, clindamycin, chloramphenicol and metro nidazole were performed by Etest in Wilkins-Chalgren agar enriched with 5% sheep blood. Motivated by some high MIC values for cefoxitin and meropenem, the cfiA gene, which codes for a metallo-beta-lactamase, was investigated among all strains, using PCR amplification. The resistance to penicillin wa s high in the samples from 1981 to 1988 (92.9%) and also in those from 1991 to 1998 (100%), although the MIC90 decreased from 256 mg/L to 24 mg/L. An increase in the resistance level to clindamycin and cefoxitin was seen from one decade to the other, the MIC90 values changing from 4 mg/L to 12 mg/L and from 8 mg/L to 32 mg/L, respectively. The susceptibility profile for me tronidazole, chloramphenicol, imipenem and meropenem remained stable, altho ugh two clinical strains showed MICs of 6 mg/L and 8 mg/L against meropenem . Almost all human intestinal strains were resistant to penicillin and all of them were susceptible to imipenem, meropenem, chloramphenicol and metron idazole. The MICs of meropenem against two strains isolated from a polluted aquatic environment were 6 mg/L and 32 mg/L. The cfiA gene was detected in five strains, two of which were isolated from clinical specimens against w hich the MIC values of cefoxitin were high and three from an aquatic enviro nment, whose susceptibility to both cefoxitin and meropenem ranged from sen sitive to resistant.