Genetic and phylogenetic analysis of avian extraintestinal and intestinal Escherichia coli.

Extraintestinal pathogenic Escherichia coli (ExPEC) isolates of animals and man are known to carry specific virulence associated genes. The intestinal tract, it is primarily colonized by various strains of commensal E. coli but it may include ExPEC as well. Here we aimed to assess possible genetic and evolutionary linkages between extraintestinal pathogenic and intestinal (commensal) E. coli of poultry. For that purpose we analysed 71 ExPEC isolates, and 40 intestinal isolates assumed to be commensal E. coli (IntEC), from dead chickens and turkey poults for 26 virulence related genes. Although the two groups shared several virulence determinants the genes pic, papC, and cdtIV were exclusively present in ExPEC and further five genes (colV, iss, kpsM, tsh and iutA), were significantly more frequent among ExPEC. Phylogenetic backgrounds of ExPEC and of IntEC isolates indicated significant differences. A 40% of ExPEC belonged to phylogroup A primarily containing strains of serogroup O78. Phylogroup D contained ExPEC strains of serogroups O53 (2 strains) and O115 (5 strains) characterized by the cdt-IV genes, suggesting the existence of new clones of avian ExPEC in phylogenetic group D. On the other hand, a 42.5% of IntEC belonged to phylogroup B1 with diverse serogroups. Our data provide insight into the clonal evolution of avian ExPEC especially in phylogenetic groups A and D, resulting avian ExPEC with similarities to human ExPEC.

Shiga toxin-producing Escherichia coli O171:H25 strain isolated from a patient with haemolytic uraemic syndrome.

Shiga toxin-producing Escherichia coli (STEC) strains of O157:H7 serotype are a predominant cause of haemolytic uraemic syndrome (HUS) worldwide, but strains of non-O157 serotypes can also be associated with serious disease. Some of them are associated with outbreaks of HUS, others with sporadic cases of HUS, and some with diarrhoea but not with outbreaks or HUS. A large number of STEC serotypes isolated from ruminants and foods have never been associated with human disease. In this study we characterize a STEC strain belonging to serotype O171:H25 that is responsible for a case of HUS. This strain has a single Shiga toxin gene encoding Stx2 toxin, and hlyA gene, but is eae-negative.