A group of international researchers have identified common virulence factors in strains of Escherichia coli collected from infected humans and chickens suggesting that avian E. coli may be a potential human pathogen. Their findings appear in the October 2006 issue of the Journal of Clinical Microbiology.
Pathogenic strains of E. coli O18:K1:H7 (ExPEC) are implicated in a range of infections in humans such as neonatal meningitis, septicemia, urinary tract infections and pneumonia. Avian E. coli pathogens (APEC) are also believed to cause urinary tract infections in cats and dogs, septicemia in calves and pigs, and systemic colibacillosis in birds. Previous studies have shown similarities between APEC and ExPEC strains but no research to date has been devoted to the comparison of specific strains for common virulence factors and genetic relationships.
O18:K1 strains are frequently isolated from humans infected with neonatal meningitis and septicemia as well as chickens with colibacillosis. The K1 capsule is a key facilitator in circumventing host defenses. IbeA, the virulence factor commonly associated with human neonatal meningitis, is also preferential in O18:K1 APEC strains. In the study twenty-two ExPEC isolates of human origin and thirty-three of avian origin were monitored and compared for their virulence factors and lethality in chicks. Both avian and human isolates proved lethal for chicks while demonstrating similar virulence patterns, one of which was identified in 75% of the isolates.
"The results obtained with the O18:K1:H7 E. coli strains that we have studied here show that various but closely related clones can be recovered from extraintestinal infections in humans and chickens," say the researchers. "Epidemiological studies are required to demonstrate if they have evolved independently or if cross-contamination between human and avian communities is possible, leading to a hypothesis that avian colibacillosis due to O18:K1:H7 strains could be considered a zoonosis."
(M. Moulin-Schouleur, C. Shouler, P. Tailliez, M.R. Kao, A. Bree, P. Germon, E. Oswald, J. Mainil, M. Blanco, J. Blanco. 2006. Common virulence factors and genetic relationships between O18:K1:H7 Escherichia coli isolates of human and avian origin. Journal of Clinical Microbiology, 44.10: 3484-3492.)
Materials provided by American Society For Microbiology. Note: Content may be edited for style and length.
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