Occurrence and analysis of rare cfiA-bft doubly positive Bacteroides fragilis strains.

We detected four cfiA-bft1 doubly positive Bacteroides fragilis strains out of 486 B. fragilis isolates analyzed for antibiotic susceptibilities and antibiotic resistance genes from a recent pan-European survey. The prevalence of the enterotoxin bft genes was roughly equal among cfiA-negative and -positive B. fragilis strains. We also demonstrated that the cfiA-bft doubly positive strains had the most common B. fragilis genomic pattern (I.1.). Thus we concluded that the bft-carrying CTn86 conjugative transposons are mobile accounting for this unexpected simultaneous occurrence of the cfiA and bft genes.