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ABSTRACTThe presence of the pathogenicity island (PAI) O122 genes, efa1(lifA), sen, pagC, nleB, and nleE, in typical and atypical enteropathogenic Escherichia coli(EPEC) strains was investigated. The simultaneous occurrence of all genes was statistically associated with diarrhea due to atypical EPEC. Detection of the complete PAI O122 could aid in the identification of potential pathogenic strains of atypical EPEC.

ABSTRACTLpf (stands for long polar fimbriae) is one of the few adhesive factors of enterohemorrhagic Escherichia coliO157:H7 associated with colonization of the intestine. E. coliO157:H7 strains possess two lpfloci encoding highly regulated fimbrial structures. Database analysis of the genes encoding the major fimbrial subunits demonstrated that they are present in commensal as well as pathogenic (both intestinal and extraintestinal) E. colistrains and in Salmonellastrains and that the lpfA1and lpfA2genes are highly prevalent among LEE (locus of enterocyte effacement)-positive E. colistrains associated with severe and/or epidemic disease. Further DNA sequence analysis of the lpfA1and lpfA2genes from different attaching-and-effacing E. colistrains has led us to the identification of several polymorphisms and the classification of the major fimbrial subunits into distinct variants. Using collections of pathogenic E. coliisolates from Europe and Latin America, we demonstrated that the different lpfAtypes are associated with the presence of specific intimin (eae) adhesin variants and, most importantly, that they are found in specific E. colipathotypes. Our results showed that the use of these fimbrial genes as markers, in combination with the different intimin types, resulted in a specific test for the identification of E. coliO157:H7, distinguishing it from other pathogenic E. colistrains.

ABSTRACTEscherichia colistrains of serotype O51:H40 were studied with regard to the presence of several virulence properties and their genetic diversity and enteropathogenicity in rabbit ileal loops. This serotype encompasses potential enteropathogenic strains mostly classified as being atypical enteropathogenic E. coli(EPEC) strains, which are genetically closer to enterohemorrhagic E. colithan to typical EPEC strains.

ABSTRACTEnterohemorrhagic Escherichia coli(EHEC) and enteropathogenic E. coli(EPEC) are diarrheagenic pathogens that colonize the gut through the formation of attaching and effacing lesions, which depend on the translocation of effector proteins via a locus of enterocyte effacement-encoded type III secretion system. Recently, two effector proteins, EspJ and TccP, which are encoded by adjacent genes on prophage CP-933U in EHEC O157:H7, have been identified. TccP consists of a unique N-terminus region and several proline-rich domains. In this project we determined the distribution of tccPin O157:H7, in non-O157 EHEC, and in typical and atypical EPEC isolates. All the EHEC O157:H7 strains tested were tccP+. Unexpectedly, tccPwas also found in non-O157 EHEC, and in typical and atypical EPEC isolates, particularly in strains belonging to serogroups O26 (EHEC), O119 (typical EPEC), and O55 (atypical EPEC). We recorded some variation in the length of tccP, which reflects diversity in the number of the proline-rich repeats. These results show the existence of a class of “attaching and effacing” pathogens which express a combination of EPEC and EHEC virulence determinants.

ABSTRACTThe correlation between various adherence patterns and adherence-related DNA sequences in Escherichia coliisolates from 1- to 4-year-old children with and without diarrhea in Sa~o Paulo, Brazil, was evaluated. A total of 1,801 isolates obtained from 200 patients and 200 age-matched controls were studied. The adherence patterns found were classified as diffuse, aggregative, aggregative in a 6-h assay, aggregative predominantly in coverslips, localized, localized-like, and noncharacteristic. In general, the DNA sequences used as probes showed excellent specificities (>93%), but their sensitivities varied. Thus, the results of bioassays and assays with DNA probes normally used to search for adherent E. colidid not correlate well, and the best method for the identification of these organisms in the clinical research setting remains controversial. Isolates presenting diffuse adherence or hybridizing with the related daaCprobe, or both, were by far the most frequent in patients (31.5, 26.0, and 23.0%, respectively), followed by isolates presenting aggregative adherence or hybridizing with the related EAEC probe, or both (21.5, 13.0, and 10.5%, respectively). None of the different combinations of adherence patterns and adherence-related DNA sequences found were associated with acute diarrhea.

ABSTRACTThe enteropathogenic role of cytolethal distending toxin-producing Escherichia coliwas investigated by searching sequences homologous to the cdtgenes of an O86 strain among 2,074 isolates from 200 children with acute diarrhea and 200 controls in Brazil. Only one (0.5%) diarrheic child and two (1.0%) nondiarrheic controls harbored cdt-positive isolates.