Extended Virulence Genotype of Pathogenic Escherichia coli Isolates Carrying the afa-8 Operon: Evidence of Similarities between Isolates from Humans and Animals with Extraintestinal Infections

Abstract

The afimbrial AfaE-VIII adhesin is common among Escherichia coli isolates from calves with intestinal and/or extraintestinal infections and from humans with sepsis or pyelonephritis. The virulence genotypes of 77 Escherichia coli afa-8 isolates from farm animals and humans were compared to determine whether any trait of commonality exists between isolates of the different host species. Over half of the extraintestinal afa-8 isolates were associated with pap and f17Ac adhesin genes and contained virulence genes (pap, hly, and cnf1) which are characteristic of human extraintestinal pathogenic E. coli (ExPEC). PapG, which occurs as three known variants (variants I to III), is encoded by the corresponding three alleles of papG. Among the pappositive strains, new papG variants (papGrs) that differed from the isolates with genes for the three adhesin classes predominated over isolates with papG allele III, which in turn were more prevalent than those with allele II. The data showed the substantial prevalence of the enteroaggregative E. coli heat-stable enterotoxin gene ( The fimbrial and afimbrial adhesins of the Afa family mediate the adherence of uropathogenic and diarrhea-associated Escherichia coli to various host tissues. Among the Afa-related surface antigens, the Afa(Dr ϩ ) adhesins (AfaE-I, AfaE-III, Dr, and F1845) bind to epithelial cells via recognition of the decay-accelerating factor (DAF; also referred to as CD55) carrying the Dr blood group antigen (15,33,36,37,44). We recently described a new afa operon (afa-8) encoding afimbrial adhesin AfaE-VIII which does not recognize DAF molecules (Afa(Dr Ϫ ) adhesin). The afa-8 operon can be either chromosome or plasmid borne, suggesting that it may be carried by a mobile element, facilitating its dissemination (16, 34). It therefore appears that in some strains the afa-8 operon is carried by a 61-kb pathogenicity island (PAI) inserted into pheV and/or pheR tRNA-encoding genes. Partial characterization of the afa-8-containing PAI indicated that this PAI carries the afa-8 operon as the only known virulence determinant (35).The afa-8 operon is common among pathogenic E. coli strains isolated from animals and humans (16,34,52). It was frequently found in animal and human isolates producing CNF toxins, but it has also been detected in CNF-negative strains isolated from calves and piglets (16,41). Bloodstream infections in which the bacteria are derived from the intestinal flora by bacterial translocation are common in patients with cancer. Preliminary results showed that the afa-8 operon is found in CNF1-producing strains associated with this type of bacteremia (22,38,42). Therefore, afa-8 is probably involved in the development of extraintestinal infections associated with primary colonization of the intestine. However, afa-8 has never been detected in diarrhea-associated human isolates (38). In addition to CNF1, certain afa-8-positive strains carry virulence factor (VF) genes including pap, sfa, f17A, and clpG (P, S, F17, and CS31A adhesins, respectively) and hlyA (...

Association of Virulence Genotype with Phylogenetic Background in Comparison to Different Seropathotypes of Shiga Toxin-Producing Escherichia coli Isolates

“…The astA gene which is widely distributed among diarrheogenic E. coli strains in humans and animals may represent an additional virulent determinant of STEC strains (15,38). Consistent with previous studies on human STEC infections (45), our study confirms the presence of the astA gene among strains carrying eae associated with HUS and outbreaks (O26:H11, O111:H2, and O157:H7).…”

Genomic analysis of the PAI ICL3 locus in pathogenic LEE-negative Shiga toxin-producing Escherichia coli and Citrobacter rodentium

“…Of these 287 STEC isolates, 44 are LEE-positive and 243 are LEE-negative. The third set comprised 77 extra-intestinal pathogenic E. coli (ExPEC) isolated from humans with bacteraemia or urinary tract infections and from calves with intestinal or extraintestinal colibacillosis (Girardeau et al, 2003). The fourth set comprised 35 ExPEC strains isolated in Scotland from lambs with nephropathy (Bertin et al, 1998).…”

Renal Collecting Duct Epithelial Cells React to Pyelonephritis-Associated Escherichia coli by Activating Distinct TLR4-Dependent and -Independent Inflammatory Pathways

“…They belong to two different O serogroups (O9 for AL511, and O101 for AL10), carry pap and afa-8 adhesin-encoding genes, and lack the hly ␣-hemolysin-encoding gene (28). In addition, the AL511 isolate carries f17Ac adhesin genes and produces factors contributing to serum resistance.…”