ARS | Publication request: LONG POLAR FIMBRIAE INVESTIGATED AS A COLONIZATION FACTOR FOR ESCHERICHIA COLI O157:H7 IN GERM-FREE PIGS

Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 13, 2001
Publication Date: N/A

Technical Abstract: The colonization mechanisms of Escherichia coli O157:H7 are not fully understood. The genome contains many homologous sequences to those of known colonization factors in other species of bacteria and these genes may be involved in the colonization by E. coli O157:H7. A sequence that encodes for long polar fimbriae (lpf) has homology with an lpf operon in Salmonella typhimurium. Long polar fimbriae facilitate colonization of murine Peyer's patches by S. typhimurium. In cell culture, E. coli O157:H7 lpf mutant was previously shown to have slightly reduced adherence and lack the ability to form microcolonies. We hypothesized that lpf is involved in colonization by E. coli O157:H7 in the germ-free pig intestine. However, results from the oral inoculation of day old germ-free pigs with 10**5 bacteria showed no difference in colonization between an E. coli O157:H7 lpf mutant and the wild-type strain. There was no difference in clinical signs, viable bacterial counts in the intestine, or the appearance and severity of the attachment and effacement lesions histologically or by electron microscopy. Thus, the lpf gene that was mutated in our lpf mutant strain was not required for colonization and pathogenicity of neonatal germ-free pigs. However, E. coli O157:H7 contains a second operon with homology to lpf genes. The lpf mutant strain used in the above experiments was constructed within the gene sequence with the greatest homology to the lpfA gene in S. typhimurium. We now suspect that the second sequence enables the original lpf mutant bacteria to produce a functional Lpf protein. Studies are ongoing to determine the effectiveness of a double lpf mutant of E. coli O157:H7 to impair colonization of germ-free pigs.