Characterization of a carbapenemase-producing clinical isolate of Bacteroides fragilis in Scandinavia: genetic analysis of a unique insertion sequence.

In 2003 a Bacteroides fragilis blood culture isolate (K2-28) was recovered from a 61-y-old male with severe general atherosclerosis during treatment with meropenem. K2-28 was shown to possess a functional metallo-beta-lactamase with a reduction in imipenem MIC from 256 to 3 mg/l in the presence of EDTA using the MBL E-test strip. PCR results were for positive for the cfiA gene. Analysis of the cfiA from K2-28 revealed it was 100% identical to previously described cfiA-1 genes. Analysis of the upstream region of cfiA revealed a novel insertion sequence (IS) element, being most similar (94% identity) to IS612 recently described from Japan designating the element within the IS4 family. The element possessed a perfect terminal inverted repeat sequence at the distal ends of the IS element and provided a putative promoter for transcription of the cfiA gene. The distance between the hybrid promoter and the cfiA start codon was 158 base pairs and inserted into a different DNA sequence upstream of cfiA to that previously reported. The -10 promoter region was most similar to that of IS613 (100%) and the -35 promoter region to IS612 (100%), demonstrating the plasticity of these genetic regions.