Evidence of Commonality between Canine and Human Extraintestinal PathogenicEscherichia coliStrains That ExpresspapGAllele III

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Abstract
Although dogs have been proposed as carriers of extraintestinal pathogenicEscherichia coli(ExPEC) with infectious potential for humans, presumed host species-specific differences between canine and human ExPEC strains have cast doubt on this hypothesis. The recent discovery that allele III ofpapG(the P fimbrial adhesin gene) predominates among human cystitis isolates and confers an adherence phenotype resembling that of canine ExPEC prompted the present reevaluation of the canine-human ExPEC connection. Sixteen pairedpap-positive urine and rectalE. coliisolates from dogs with urinary tract infection were studied.papG(adhesin) andpapA(pilin) allele type, agglutination phenotypes, virulence factor genotypes, and randomly amplified polymorphic DNA and pulsed-field gel electrophoresis fingerprints were analyzed and compared with those of human ExPEC controls. The 16 canine strains contained predominantlypapGallele III. Agglutination phenotypes segregated strictly according topapGallele status and were homogeneous among strains with the samepapGallele profile irrespective of their human versus canine origin. Canine and human PapG variant III peptide sequences were highly homologous, without host species-specific differences. The most prevalent caninepapAallele was F48, a novel variant recently identified among human urosepsis isolates. In addition topap, human ExPEC-associated virulence genes detected among the canine strains includedsfa/focDE,sfaS,fyuA,hlyA,cnf1,cdtB,kpsMT-II and -III,rfc,traT,ompT, and a marker for a pathogenicity-associated island from archetypal human ExPEC strain CFT073. Molecular fingerprinting confirmed the fecal origin of all but one canine urine isolate and showed one pair of O6 canine urine and fecal isolates to be extremely similar to an O6 human urosepsis isolate with which they shared all other genotypic and phenotypic characteristics analyzed. These data demonstrate that canine ExPEC strains are similar to, and in some instances essentially indistinguishable from, human ExPEC strains, which implicates dogs and their feces as potential reservoirs ofE. coliwith infectious potential for humans.