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Contribution of the SitABCD, MntH, and FeoB Metal Transporters to the Virulence of Avian Pathogenic Escherichia coli O78 Strain 7122

INRS-Institut Armand-Frappier, Laval, Québec, Canada,¹ INRA, Centre de Tours, Infectiologie Animale et Santé Publique UR1282, 37380 Nouzilly, France,² Center for Infectious Diseases, The Biodesign Institute, Arizona State University, Tempe, Arizona 85287,³ Department of Biology, Washington University, St. Louis, Missouri 63130⁴

Received 8 June 2007/ Returned for modification 25 July 2007/ Accepted 5 November 2007

The roles of SitABCD, MntH, and FeoB metal transporters in the virulence of avian pathogenic Escherichia coli (APEC) O78 strain 7122 were assessed using isogenic mutants in chicken infection models. In a single-strain infection model, compared to 7122, the sit strain demonstrated reduced colonization of the lungs, liver, and spleen. Complementation of the sit strain restored virulence. In a coinfection model, compared to the virulent APEC strain, the sit strain demonstrated mean 50-fold, 126-fold, and 25-fold decreases in colonization of the lungs, liver, and spleen, respectively. A mntH sit strain was further attenuated, demonstrating reduced persistence in blood and mean 1,400-fold, 954-fold, and 83-fold reduced colonization in the lungs, liver, and spleen, respectively. In coinfections, the feoB sit strain demonstrated reduced persistence in blood but increased colonization of the liver. The mntH, feoB, and feoB mntH strains were as virulent as the wild type in either of the infection models. Strains were also tested for sensitivity to oxidative stress-generating agents. The mntH sit strain was the most sensitive strain and was significantly more sensitive than the other strains to hydrogen peroxide, plumbagin, and paraquat. sit sequences were highly associated with APEC and human extraintestinal pathogenic E. coli compared to commensal isolates and diarrheagenic E. coli. Comparative genomic analyses also demonstrated that sit sequences are carried on conjugative plasmids or associated with phage elements and were likely acquired by distinct genetic events among pathogenic E. coli and Shigella sp. strains. Overall, the results demonstrate that SitABCD contributes to virulence and, together with MntH, to increased resistance to oxidative stress.

Published ahead of print on 19 November 2007.

Editor: J. B. Bliska