Distribution of the cfiA Gene among Bacteroides fragilis Strains in Japan and Relatedness of cfiA to Imipenem Resistance

The cfiA gene, encoding an imipenem-hydrolyzing metallo-β-lactamase produced by Bacteroides fragilis, and insertion-like elements were detected by PCR amplification with B. fragilis strains isolated in Japan. The cfiA gene was found in 1.9 and 4.1% of the imipenem-susceptible B. fragilis isolates collected from 1987 to 1988 and from 1992 to 1994, respectively. Insertion-like elements adjacent to the cfiA gene were found in all nine metallo-β-lactamase-producing imipenem-resistant strains tested but not in nine cfiA-positive strains with no detectable metallo-β-lactamase activity.