Evidence of commonality between canine and human extraintestinal pathogenic Escherichia coli strains that express papG allele III

Although dogs have been proposed as carriers of extraintestinal pathogenic Escherichia coli (ExPEC) with infectious potential for humans, presumed hos t species-specific differences between canine and human ExPEC strains have cast doubt on this hypothesis. The recent discovery that allele III of papG (the P fimbrial adhesin gene) predominates among human cystitis isolates a nd confers an adherence phenotype resembling that of canine ExPEC prompted the present reevaluation of the canine-human ExPEC connection. Sixteen pair ed pap-positive urine and rectal E. coli isolates from dogs with urinary tr act infection were studied. papG (adhesin) and papA (pilin) allele type, ag glutination phenotypes, virulence factor genotypes, and randomly amplified polymorphic DNA and pulsed-field gel electrophoresis fingerprints were anal yzed and compared with those of human ExPEC controls. The 16 canine strains contained predominantly papG allele LII. Agglutination phenotypes segregat ed strictly according to papG allele status and were homogeneous among stra ins with the same papG allele profile irrespective of their human versus ca nine origin. Canine and human PapG variant LII peptide sequences were highl y homologous, without host species-specific differences. The most prevalent canine papA allele was F48, a novel variant recently identified among huma n urosepsis isolates. In addition to pap, human ExPEC-associated virulence genes detected among the canine strains included sfa/focDE, sfaS, fyuA, hly A, cnf1, cdtB, kpsMT-II and -III, rfc, traT, ompT and a marker for a pathog enicity-associated island from archetypal human ExPEC strain CFT073, Molecu lar fingerprinting confirmed the fecal origin of all but one canine urine i solate and showed one pair of O6 canine urine and fecal isolates to be extr emely similar to an O6 human urosepsis isolate with which they shared all o ther genotypic and phenotypic characteristics analyzed. These data demonstr ate that canine ExPEC strains are similar to, and in some instances essenti ally indistinguishable from, human ExPEC strains? which implicates dogs and their feces as potential reservoirs of E. coli with infectious potential f or humans.