Tânia A. T. Gomes

10.321/eid0805.Typical and Atypical Enteropathogenic Escherichia coli

Typical and atypical enteropathogenic Escherichia coli (EPEC) strains differ in several characteristics. Typical EPEC, a leading cause of infantile diarrhea in developing countries, is rare in industrialized countries, where atypical EPEC seems to be a more important cause of diarrhea. For typical EPEC, the only reservoir is humans; for atypical EPEC, both animals and humans can be reservoirs. Typical and atypical EPEC also differ in genetic characteristics, serotypes, and virulence properties. Atypical EPEC is more closely related to Shiga toxin–producing E. coli (STEC), and like STEC these strains appear to be emerging pathogens.

Phenotypic and Genotypic Characteristics of Escherichia coli Strains of Non–Enteropathogenic E. coli (EPEC) Serogroups that Carry eae and Lack the EPEC Adherence Factor and Shiga Toxin DNA Probe Sequences

This study was conducted to characterize the virulence potential of 59 Escherichia coli strains carrying EAE and lacking the enteropathogenic E. coli adherence factor and Shiga toxin probe sequences. In hybridization studies, all strains carried the locus of enterocyte effacement (LEE)-associated DNA sequences. Of the other 15 virulence DNA sequences tested, HLY was the most frequent (44.1%); 17 combinations of these sequences were found, but strains carrying EAE only (EAE profile) were the most frequent (35.6%). Except for 1 cytodetaching strain, all others adhered to HeLa and Caco-2 cells, most of which (approximately 75.0%) showed variations of the localized adherence pattern. Actin accumulation was detected in 75.9% of the nondetaching strains. Most strains had LEE, probably inserted in pheU (49.2%), and presented a nontypeable intimin (83.1%). Translocated intimin receptor-derived DNA sequences correlated with enteropathogenic and enterohemorrhagic E. coli in 61.0% and 32.0% of the strains, respectively. Thirty-five different serotypes were found. Only strains with the EAE profile were associated with diarrhea (P=.039).

Emerging enteropathogenic Escherichia coli strains

Escherichia coli strains of nonenteropathogenic serogroups carrying eae but lacking the enteropathogenic E. coli adherence factor plasmid and Shiga toxin DNA probe sequences were isolated from patients (children, adults, and AIDS patients) with and without diarrhea in Brazil. Although diverse in phenotype and genotype, some strains are potentially diarrheagenic.

Prevalence of diarrheagenic Escherichia coli in children with diarrhea in Salvador, Bahia, Brazil

We report the frequency of the different diarrheagenic Escherichia coli (DEC) categories isolated from children with acute endemic diarrhea in Salvador, Bahia. The E. coli isolates were investigated by colony blot hybridization with the following genes probes: eae, EAF, bfpA, Stx1, Stx2, ST-Ih, ST-Ip, LT-I, LT-II, INV, and EAEC, as virulence markers to distinguish typical and atypical EPEC, EHEC/STEC, ETEC, EIEC, and EAEC. Seven of the eight categories of DEC were detected. The most frequently isolated was atypical EPEC (10.1%) followed by ETEC (7.5%), and EAEC (4.2%). EHEC, STEC, EIEC, and typical EPEC were each detected once. The strains of ETEC, EAEC, and atypical EPEC belonged to a wide variety of serotypes. The serotypes of the others categories were O26:H11 (EHEC), O21:H21 (STEC), O142:H34 (typical EPEC), and O:H55 (EIEC). We also present the clinical manifestations and other pathogenic species observed in children with DEC. This is the first report of EHEC and STEC in Salvador, and one of the first in Brazil.

Virulence Properties and Characteristics of Shiga Toxin-Producing Escherichia coli in São Paulo, Brazil, from 1976 through 1999

ABSTRACT Twenty-nine Shiga toxin-producing Escherichia coli (STEC) strains were identified in a collection of 2,607 isolates from patients with diarrhea in São Paulo, Brazil, from 1976 to 1999. The STEC strains belonged mainly to serotypes O111:HNM (HNM, nonmotile) (13 of 29 [44.8%]), O111:H8 (7 of 29 [24%]), and O26:H11 (4 of 29 [13.8%]); stx1eae (26 of 29 [89.6%]), in combination with either enterohemorrhagic E. coli hlyA (11 of 26 [42%]) or astA (24 of 26 [92.3%]), prevailed. The O111 STEC strains were distinguished by their inability to decarboxylate lysine. The predominance of STEC O111 and O26 since the late 1970s and the identification of STEC serotypes O55:H19, O93:H19, and O118:H16 in association with human infections in Brazil are described for the first time.

Clinical significance of Escherichia albertii.

Discriminating Escherichia albertii from other Enterobacteriaceae is difficult. Systematic analyses showed that E. albertii represents a substantial portion of strains currently identified as eae-positive Escherichia coli and includes Shiga toxin 2f–producing strains. Because E. albertii possesses the eae gene, many strains might have been misidentified as enterohemorrhagic or enteropathogenic E. coli.

Distribution of tccP in Clinical Enterohemorrhagic and Enteropathogenic Escherichia coli Isolates

ABSTRACT Enterohemorrhagic 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 tccP in O157:H7, in non-O157 EHEC, and in typical and atypical EPEC isolates. All the EHEC O157:H7 strains tested were tccP+. Unexpectedly, tccP was 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.

Combinations of putative virulence markers in typical and variant enteroaggregative Escherichia coli strains from children with and without diarrhoea

Enteroaggregative Escherichia coli (EAEC) is defined by the ability to produce aggregative adherence (AA) to cultured cells. We analysed 128 EAEC strains, isolated from children with and without diarrhoea, regarding the presence of 11 EAEC virulence genes. Seventy strains carried and 58 lacked the EAEC probe sequence; 17 probe positive and 31 probe negative strains showed variations in the AA pattern. All EAEC probe positive strains carried at least one EAEC marker; aspU (94.3%), irp2 (91.4%), and aggR (74.3%) were the most prevalent. Conversely, among the EAEC probe negative strains, 41.4% were devoid of any marker and astA predominated (44.8%). No significant statistical difference in the prevalence of any marker between cases and controls in both EAEC probe groups or AA variants was found. We suggest that the EAEC probe positive strains may have a higher pathogenic potential or alternatively, EAEC probe negative strains may harbour virulence factors as yet undescribed.

Genes Related to Long Polar Fimbriae of Pathogenic Escherichia coli Strains as Reliable Markers To Identify Virulent Isolates

ABSTRACT Lpf (stands for long polar fimbriae) is one of the few adhesive factors of enterohemorrhagic Escherichia coli O157:H7 associated with colonization of the intestine. E. coli O157:H7 strains possess two lpf loci 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. coli strains and in Salmonella strains and that the lpfA1 and lpfA2 genes are highly prevalent among LEE (locus of enterocyte effacement)-positive E. coli strains associated with severe and/or epidemic disease. Further DNA sequence analysis of the lpfA1 and lpfA2 genes from different attaching-and-effacing E. coli strains 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. coli isolates from Europe and Latin America, we demonstrated that the different lpfA types are associated with the presence of specific intimin (eae) adhesin variants and, most importantly, that they are found in specific E. coli pathotypes. 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. coli O157:H7, distinguishing it from other pathogenic E. coli strains.

Diversity of virulence profiles of Shiga toxin-producing Escherichia coli serotypes in food-producing animals in Brazil

The prevalence, serotypes and virulence profiles of Shiga toxin-producing Escherichia coli (STEC) were investigated in 205 healthy beef and dairy cattle, and 106 goats reared in the southeastern region of Minas Gerais State, Brazil. The prevalence of STEC was 57.5% (61/106) in goats, 39.2%, (40/102) in beef cattle and 17.5% (18/103) in dairy cattle. Among the 514 STEC isolates, 40 different serotypes were found and some of them were identified in a specific host. STEC isolates harboring stx1 corresponded to 15.6% (28/180), 26.7% (16/60) and 24.1% (66/274) in beef cattle, dairy cattle and goats, respectively. stx2 was found in 30% (54/180), 53.3% (32/60) and 34.7% (95/274) of beef and dairy cattle, and goats. stx1 plus stx2 sequences were harbored by 54.4% (98/180), 20% (12/60) and 41.2% (113/274) of beef cattle, dairy cattle and goats, respectively. The eae sequence was found in 15% (9/60) and 0.6% (1/180) of STEC isolates from dairy and beef cattle, respectively, and the toxB gene was found only in one O157:H7 strain isolated from beef cattle. Strains with the genetic profiles stx2 ehxA iha saa and stx1 stx2 ehxA iha saa were the most prevalent among STEC isolates from cattle. Profiles stx1 stx2 ehxA iha, stx2, and stx1 iha accounted for 75.5% (207 /274) of the STEC isolates from goats. While STEC strains carrying either stx2 alone or associated with stx1 were found more frequently in cattle, those harboring sequences stx1c and stx2d alone or associated with stx1c predominated in goats. Our data show a diversity of STEC strains in food-producing animals, most of them carrying genes linked to severe forms of human diseases.