DISTRIBUTION OF THE BUNDLE-FORMING PILUS STRUCTURAL GENE (BFPA) AMONGENTEROPATHOGENIC ESCHERICHIA-COLI

Enteropathogenic Escherichia coli (EPEC) express an inducible bundle-f orming pilus (BFP) associated with the presence of the EPEC adherence factor (EAF) plasmid and localized adherence (LA) on HEp-2 cells. rhe cloned structural gene (bfpA) encoding BFP was found to be specific fo r EPEC, as homologous sequences were found only in EPEC and not in oth er enteropathogens. The bfpA probe was slightly more sensitive than th e EAF probe; among EPEC strains with LA, the bfpA and EAF probes hybri dized with 99% and 96% of the strains, respectively. Immunoblotting of whole cell lysates of BFP-positive, EAF-positive or -negative, and LA -positive or -negative EPEC strains revealed variations in the size (1 8,500-21,000) of the expressed structural subunit of BFP, suggesting d ifferences in processing that may account for discrepancies between th e bfpA, EAF, and LA. Because the bfpA probe consists primarily of sequ ences encoding an important EPEC virulence factor, in contrast to the unknown function of sequences contained in the EAF probe, the bfpA pro be may be useful in epidemiologic studies to detect EPEC.