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

We detected four cfiAebft1 doubly positive Bacteroides fragilis strains out of 486 B. fragilis isolates analyzed for antibiotic susceptibilities and antibiotic resistance genes from a recent pan-European sur- vey. The prevalence of the enterotoxin bft genes was roughly equal among cfiA-negative and -positive B. fragilis strains. We also demonstrated that the cfiAebft 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.