Expression of the carbapenemase gene (cfiA) in Bacteroides fragilis.

Bacteroides fragilis strains were studied to examine carbapenemase gene (cfiA) expression and insertion sequence (IS) element promoters. High-level resistance was associated with high meropenemase activity and IS elements upstream of cfiA. Sequencing revealed two element types; IS1187 and elements related to IS942 and IS1170. The latter was implicated in the conversion to carbapenem resistance in a cfiA-positive isolate during imipenem therapy. Two strains showing low-level resistance, and strains susceptible to meropenem, did not possess IS elements upstream of cfiA. The prevalence in Nottingham of clinical isolates of B. fragilis with cfiA and efficient IS element promoters was low (0.6%).