Identification of a third metalloprotease toxin gene in extraintestinal isolates of Bacteroides fragilis

To further understand the epidemiology of enterotoxigenic Bacteroides fragi lis (ETBF), 89 extraintestinal B. fragilis strains from Seoul, Korea, were examined for secretion of B. fragilis toxin (BFT) by the HT29/C1 biologic a ssay and for the B. fragilis toxin gene (bft) by colony blot hybridization and PCR. Complete agreement between the three techniques was found. Overall , 34 B. fragilis strains (38%) were identified as ETBF. Eleven of the 34 ET BF strains (32%) expressed a new isoform of BFT (Korea-BFT). This new isofo rm is more related to BFT-2 than to BFT-1. Like BFT-1 and BFT-2, Korea-BFT cleaves E-cadherin, the zonula adherens protein.