Molecular characterization of imipenem-resistant, cfiA-positive Bacteroides fragilis isolates from the USA, Hungary and Kuwait

Abstract

FifteenBacteroides fragilisisolates from the USA, Hungary and Kuwait were examined for carbapenem resistance, for carbapenemase activity and, with the use of various PCR-based methods and nucleotide sequencing, forcfiAgenes and activating insertion sequence (IS) elements. All theB. fragilisisolates werecfiA-positive, 10 of thecfiAgenes being upregulated by IS elements that are already known. Of these 10, one was of a novel type (designated IS943) and two further ones (IS614B and IS614C) were suspected hybrids of IS612, IS614and IS942. There were fivecfiA-positive imipenem-resistantB. fragilisisolates with elevated imipenem MICs (minimal inhibitory concentration) that harboured no IS insertion upstream of thecfiAgene, but produced carbapenemase; these isolates might possess a novel activation mechanism. On the basis of the available phenotypic and genotypic evidence, the present data suggest that there are at least twocfiAactivation mechanisms amongB. fragilisisolates.