In three geographically diverse communities, a single clonal group accounted for nearly half of community-acquired urinary tract infections in women that were caused by E. coli strains with resistance to trimethoprim-sulfamethoxazole. The widespread distribution and high prevalence of E. coli clonal group A has major public health implications.

Retail foods may be an important vehicle for community-wide dissemination of antimicrobial-resistant E. coli and ExPEC, which may represent a newly recognized group of medically significant foodborne pathogens.

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Although dogs have been proposed as carriers of extraintestinal pathogenic Escherichia 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 of papG (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 paired pappositive urine and rectal E. coli isolates from dogs with urinary tract infection were studied. papG (adhesin) and papA (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 predominantly papG allele III. Agglutination phenotypes segregated strictly according to papG allele status and were homogeneous among strains with the same papG allele 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 canine papA allele was F48, a novel variant recently identified among human urosepsis isolates. In addition to pap, human ExPEC-associated virulence genes detected among the canine strains included sfa/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 of E. coli with infectious potential for humans.

The phylogenetic distributions of multiple putative virulence factors (VFs) and papA (P fimbrial structural subunit) alleles among 182 Escherichia coli blood isolates from patients with diverse-source bacteremia were defined. Phylogenetic correspondence among these strains, the E. coli Reference (ECOR) collection, and other collections of extraintestinal pathogenic E. coli (ExPEC) was assessed. Although among the 182 bacteremia isolates phylogenetic group B2 predominated, exhibited the greatest concentration of individual VFs, and contained the largest number of familiar virulent clones, other phylogenetic groups exhibited greater concentrations of certain VFs than did group B2 and included several additional virulent clones. Certain of the newly detected VF genes, e.g., fyuA (yersiniabactin; 76%) and focG (F1C fimbriae; 25%), were as prevalent or more prevalent than their more familiar traditional counterparts, e.g., iut (aerobactin; 57%) and sfaS (S fimbriae; 14%), thus possibly offering additional useful targets for preventive interventions. Considerable diversity of VF profiles was observed at every level within the phylogenetic tree, including even within individual lineages. This suggested that many different pathways can lead to extraintestinal virulence in E. coli and that the evolution of ExPEC, which involves extensive horizontal transmission of VFs and continuous remodeling of pathogenicityassociated islands, is a highly active, ongoing process.The strains of Escherichia coli that cause extraintestinal infections such as urinary tract infection (UTI), meningitis, and bacteremia are distinct both from most intestinal commensal E. coli types and from diarrheagenic E. coli types (13,57,65,70). These specialized extraintestinal pathogenic E. coli (ExPEC) strains (65) are thought to derive primarily from E. coli phylogenetic group B2 (as defined within the E. coli Reference [ECOR] collection by multilocus enzyme electrophoresis [MLEE]) (20,54) and to acquire their unique pathogenicity from their distinctive virulence factors (VFs) (4,10,59,60).Putative VFs of ExPEC include diverse adhesins, toxins, polysaccharide coatings (including capsules and lipopolysaccharides), siderophores, serum resistance mechanisms, and invasins (21,33,70). Such VFs help the organisms colonize host surfaces, avoid and/or subvert host defense mechanisms, injure and/or invade host cells and tissues, and incite a noxious inflammatory response, thereby giving rise to clinical disease (12, 21, 70). The VF genes of ExPEC are thought to be primarily inherited vertically within evolutionary lineages but also to be transferred horizontally between lineages, in some instances on plasmids or on "pathogenicity-associated islands" (PAIs), which are gene blocks that contain multiple contiguous VF genes (2,10,16,18,36,50,61). Better understandings of the prevalence and evolutionary origins of the VFs of ExPEC and of the distinctive "virulent clones" that make up the ExPEC population should hasten the development of the preventive measures that...

Seventy cerebrospinal fluid Escherichia coli isolates from infants with neonatal bacterial meningitis (NBM), as submitted to the Netherlands Reference Laboratory for Bacterial Meningitis from 1989 through 1997, were assessed for phylogenetic background and extended virulence genotypes, in comparison with the E. coli reference collection, by using molecular methods. Phylogenetic group B2 significantly predominated overall (81%). The 4 major phylogenetic clusters exhibited distinctive virulence genotypes, suggesting diverse evolutionary histories for the individual genes. Many genes not previously studied in NBM, notably diarrhea-associated cdtB (cytolethal distending toxin [46%]) and urinary tract infection-associated ompT (outer membrane protease T [96%]), were as or more prevalent than traditional NBM-associated traits, such as ibeA (invasion of brain endothelium [33%]), sfaS (S fimbriae [59%]), and K1 capsule (81%). These findings provide novel insights into the phylogenetic origins of NBM-associated E. coli and suggest numerous new potential targets for preventive interventions against this dire disease.

Polymorphisms in PapA, the major structural subunit and antigenic determinant of P fimbriae of extraintestinal pathogenic Escherichia coli, are of considerable epidemiological, phylogenetic, and immunotherapeutic importance. However, to date, no method other than DNA sequencing has been generally available for their detection. In the present study, we developed and rigorously validated a novel PCR-based assay for the 11 recognized variants of papA and then used the new assay to assess the prevalence, phylogenetic distribution, and bacteriological associations of the papA alleles among 75 E. coli isolates from patients with urosepsis. In comparison with conventional F serotyping, the assay was extremely sensitive and specific, evidence that papA sequences are highly conserved within each of the traditionally recognized F serotypes despite the diversity observed among F types. In certain strains, the assay detected serologically occult copies of papA, of which some were shown to represent false-negative serological results and others were shown to represent the presence of nonfunctional pap fragments. Among the urosepsis isolates, the assay revealed considerable segregation of papA alleles according to O:K:H serotype, consistent with vertical transmission within clones, but with exceptions which strongly suggested horizontal transfer of papA alleles between lineages. Sequencing of papA from two strains that were papA positive by probe and PCR but F negative in the new PCR assay led to the discovery of two novel papA variants, one of which was actually more prevalent among the urosepsis isolates than were several of the known papA alleles. These findings provide novel insights into the papA alleles of extraintestinal pathogenic E. coli and indicate that the F PCR assay represents a versatile new molecular tool for epidemiological and phylogenetic investigations which should make rapid, specific detection of papA alleles available to any laboratory with PCR capability.

Repetitive-element PCR (rep-PCR) fingerprinting is a promising molecular typing tool for Escherichia coli, including for discriminating between pathogenic and nonpathogenic clones, but is plagued by irreproducibility. Using the ERIC2 and BOXA1R primers and 15 E. coli strains from the ECOR reference collection (three from each phylogenetic group, as defined by multilocus enzyme electrophoresis [MLEE], including virulence-associated group B2), we rigorously assessed the effect of extremely elevated annealing temperatures on rep-PCR's reproducibility, discriminating power, and ability to reveal MLEE-defined phylogenetic relationships. Modified cycling conditions significantly improved assay reproducibility and discriminating power, allowing fingerprints from different cyclers to be analyzed together with minimal loss of resolution. The correspondence of rep-PCR with MLEE with respect to tree structure and regression analysis of distances was substantially better with modified than with standard cycling conditions. Nonetheless, rep-PCR was only a fair surrogate for MLEE, and when fingerprints from different days were compared, it failed to distinguish between different clones within all-important phylogenetic group B2. These findings indicate that although the performance and phylogenetic fidelity of rep-PCR fingerprinting can be improved substantially with modified assay conditions, even when so improved rep-PCR cannot fully substitute for MLEE as a phylogenetic typing method for pathogenic E. coli.Escherichia coli, the most frequent cause of urinary tract infections, neonatal sepsis and meningitis, and bacterial infectious diarrhea, is responsible for an enormous burden of morbidity, mortality, and health care costs (14,15,25,33,40,41,46,48). Paradoxically, as the predominant facultative member of the normal human colonic flora, E. coli is present in most individuals as a harmless commensal (48). Pathogenic and commensal strains of E. coli to a large extent derive from separate evolutionary groups within the highly clonal E. coli population (8,42,45). Strains from lineages associated with pathogenecity typically possess specific virulence traits which confer the ability to cause disease in intact hosts (6,24,27,37,42,46). These virulence traits are inherited vertically within the resulting virulent clones (27,37,46,51) but also can be transmitted horizontally to other lineages (2,27,36,37,43), sometimes as part of blocks of virulence genes known as pathogenicity-associated islands (4,5,21,22,31,50).Investigation of E. coli virulence in relation to population structure requires a genotyping method that can reveal underlying genetic relationships between different E. coli strains. Traditional O, K, and H serotypes, plasmid profiles, and biotypes in general are unreliable indicators of clonal relationships (9, 13, 45, 54). In contrast, electrophoretic mobility patterns for multiple metabolic enzymes (multilocus enzyme electrophoresis [MLEE]), DNA sequence analysis of such housekeeping genes, and restriction fragment ...