A GENE-CLUSTER CLOSELY-RELATED TO TYPE-II SECRETION PATHWAY OPERONS OF GRAM-NEGATIVE BACTERIA IS LOCATED ON THE LARGE PLASMID OF ENTEROHEMORRHAGIC ESCHERICHIA-COLI O157 STRAINS

Analysis of 14.162 kb of DNA derived from plasmid pO157 of enterohemor rhagic Escherichia coli (EHEC) O157:H7 strain EDL933, extending in the 5' direction of the recently described EHEC-hly operon, revealed 13 o pen reading frames (ORF) which showed great similarities to genes of m embers of the type II pathway secretion systems of Gram-negative bacte ria. We named the ORFs etpC to etpO for EHEC type II secretion pathway In addition, an IS911-like insertion element was found to separate th e etp genes from the EHEC hlyC gene. Hybridization experiments with a specific etp probe and various categories of enteric E. coli pathotype s revealed that the etp gene cluster occurred in all 30 EHEC strains o f serogroup O157 (100%) tested and is distributed sporadically among o ther EHEC serogroups (60%). In addition, the etp genes were rarely det ected in STEC isolated from bovine feces (10%). Moreover, it was found not to occur in enteropathogenic E. coli, enteroaggregative E. coli, enterotoxigenic E. coli and enteroinvasive E. coli. The results obtain ed with the erp probe were confirmed by a PCR approach to specifically detect an internal fragment of the etpD gene.