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Journal of Clinical Microbiology, April 2003, p. 1375-1385, Vol. 41, No. 4
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.4.1375-1385.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Presence and Characterization of Extraintestinal Pathogenic Escherichia coli Virulence Genes in F165-Positive E. coli Strains Isolated from Diseased Calves and Pigs

Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire,¹ Département de Microbiologie et Immunologie, Faculté de Médecine, Université de Montréal, Saint-Hyacinthe,³ Environmental Biotechnology Sector, Biotechnology Research Institute, National Research Council of Canada, Montreal, Québec, Canada²

Received 11 January 2002/ Returned for modification 22 September 2002/ Accepted 15 December 2002

The virulence genotype profile and presence of a pathogenicity island(s) (PAI) were studied in 18 strains of F165-positive Escherichia coli originally isolated from diseased calves or piglets. On the basis of their adhesion phenotypes and genotypes, these extraintestinal pathogenic strains were classified into three groups. The F165 fimbrial complex consists of at least two serologically and genetically distinct fimbriae: F165₁ and F165₂. F165₁ is encoded by the foo operon (pap-like), and F165₂ is encoded by fot (sfa related). Strains in group 1 were foo and fot positive, strains in group 2 were foo and afa positive, and strains in group 3 were foo positive only. The strains were tested for the presence of virulence genes found mainly in extraintestinal pathogenic E. coli (ExPEC) strains. Although all the strains were positive for the papA variant encoding F11 fimbriae incD, traT, and papC, the prevalence of virulence genes commonly found in PAIs associated with ExPEC strains was highly variable, with strains of group 2 harboring most of the virulence genes tested. papG allele III was detected in all strains in group 1 and in one strain in group 3. All other strains were negative for the known alleles encoding PapG adhesins. The association of virulence genes with tRNA genes was characterized in these strains by using pulsed-field gel electrophoresis and DNA hybridization. The insertion site of the foo operon was found at the pheU tRNA locus in 16 of the 18 strains and at the selC tRNA locus in the other 2 strains. Furthermore, 8 of the 18 strains harbored a high-pathogenicity island which was inserted in either the asnT or the asnV/U tRNA locus. These results suggest the presence of one or more PAIs in septicemic strains from animals and the association of the foo operon with at least one of these islands. F165-positive strains share certain virulence traits with ExPEC, and most of them are pathogenic in piglets, as tested in experimental infections.

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