Bacteroides fragilis are both key commensals and important human pathogens. Particular
strains of B. fragilis, termed enterotoxigenic B. fragilis (ETBF), are recently identified enteric
pathogens of children and adults. These strains are distinguished by secretion of a 20kDa
metalloprotease toxin (B. fragilis toxin or BFT), the first recognized and only established toxin
to date for B. fragilis. Three isotypes of BFT are encoded by distinct bft loci contained within a
6kb chromosomal region unique to ETBF strains termed the B. fragilis pathogenicity island …