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 enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain EDL933, extending in the 5' direction of the recently described EHEC-hly operon, revealed 13 open reading frames (ORF) which showed great similarities to genes of members of the type II pathway secretion systems of Gram-negative bacteria. We named the ORFs etpC to etpO for EHEC type II secretion pathway In addition, an IS911-like insertion element was found to separate the etp genes from the EHEC hlyC gene. Hybridization experiments with a specific etp probe and various categories of enteric E. coli pathotypes revealed that the etp gene cluster occurred in all 30 EHEC strains of serogroup O157 (100%) tested and is distributed sporadically among other EHEC serogroups (60%). In addition, the etp genes were rarely detected 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 obtained with the erp probe were confirmed by a PCR approach to specifically detect an internal fragment of the etpD gene.