Bacteroides fragilis is a Gram negative nonsporulating anaerobic rod bacterium that
makes up about 1 to 2% of the normal human colonic microflora. In 1984, Myer et al.
reported that some strains of B. fragilis produce enterotoxin and cause diarrheal disease
in cattle and human. Since then it has been termed enterotoxigenic B. fragilis (ETBF).
In this study, we tried to detect enterotoxin gene from 37 B. fragilis strains, isolated in
Korean patients, to confirm the existence of ETBF and usefulness of PCR as a rapid
diagnosis method. By this method, we identified 9 ETBF strains and confirmed their
pathogenesis by cytotoxicity test. No significant cross-reactivity with other anaerobes or
aerobes was observed. Thus, the PCR method may be considered useful for the
sensitive and rapid detection of anaerobic infections. And the entire amplified PCR
mixture was ligated into a pT7Blue T-vector and transformed into E. coli. When the
nucleotide sequences of cloned PCR products were compared with reported enterotoxin
gene, pBF529 inserted DNA sequence was nearly in good agreement with it but pBF570
inserted DNA sequence showed some difference at nucleotide 270-300. A search for
nucleotide sequence homologies revealed that pBF529 exhibited 99%, but pBF570
indicated only 90% identity with reported enterotoxin gene. According to these results, it
was suggested that ETBF toxin can be differentiated into at least 2 subtypes.