Reduced Etiological Role for Enteropathogenic Escherichia coli in Cases of Diarrhea in Brazilian Infants

Abstract

Previously common in Brazil, enteropathogenic Escherichia coli (EPEC) strains of serogroups O55, O111, and O119 are now rare, while enteroadherent strains other than EPEC, belonging to serogroups such as O125, were prevalent among 126 diarrheic infants less than 1 year old who were surveyed. None of these strains had the EPEC bundle-forming pilus (bfpA) gene.A number of organisms, including viral, protozoan, and bacterial agents, are associated with the etiology of infantile infectious diarrhea, a leading cause of infantile mortality and morbidity worldwide. Although representing a common species of the human intestinal microbiota, Escherichia coli is also considered an important bacterial agent of infantile infectious diarrhea, an association first described in the report of John Bray (2), when enteropathogenic E. coli (EPEC) was found as the cause of a diarrhea outbreak originating from a pediatric nursery in London, United Kingdom, in 1945. In addition to EPEC, five other diarrheagenic E. coli (DEC) pathotypes were later described: enterotoxigenic (ETEC), enteroinvasive (EIEC), enterohemorrhagic (EHEC), enteroaggregative (EAEC), and diffusely adhering (DAEC) E. coli. ETEC, EAEC, and EHEC are toxin producers; EPEC, EAEC, and DAEC express characteristic adhesion patterns (localized, aggregative, and diffuse, respectively) to epithelial cells and are thus referred to as enteroadherent E. coli; EIEC is distinguished by the capacity to invade epithelial cells and the inability to produce toxins. Serotyping, screening for pathogenicity factors, and adherence to cultured epithelial cells comprise the main laboratorial diagnosis tools for diarrhea caused by DEC. For a detailed review of DEC, see reference 12.In a recent survey carried out to investigate DEC prevalence in Botucatu, São Paulo State, Brazil, a region where some of the first epidemiological studies of enteropathogenic enterobacteria in Brazil were conducted (10), EAEC and rotavirus were found to be dominant, while traditional (EPEC, ETEC, EIEC, and EHEC) DEC pathotypes were absent from the stools of diarrheic children less than 13 years old (14). In order to better assess the role of EAEC in diarrhea and confirm the absence of EPEC in this population, we carried out the present study, restricting the survey to patients less than 1 year old, an age group more susceptible than others to EPEC-related diarrhea. The patient group consisted of 126 infants who attended the UNESP Hospital and the Medical Training Center of Botucatu between 1997 and 2000, with a record of at least two daily episodes of fluid stool evacuations, associated or not with vomiting, for 3 days or more. A total of 39 age-and geographically matched controls, randomly chosen at the same time among healthy volunteers in the community, were also surveyed. The stool collection was performed with the consent of the infant's family and the approval of the Hospital Committee on Ethics in Research. According to conventional bacteriological procedures, one to three out of five colonies randomly pi...

Typical Enteroaggregative and Atypical Enteropathogenic Types of Escherichia coli Are the Most Prevalent Diarrhea-Associated Pathotypes among Brazilian Children

“…As demonstrated in this and previous work, EAEC appears to have become a major etiologic agent of diarrhea in São Paulo. Several other studies conducted in Brazil have also shown that EAEC strains are frequently detected in children with diarrhea (4,13,14,15,16,25). Taken together, these findings suggest that EAEC is emerging as a significant enteric pathogen, responsible for acute and persistent diarrhea in Brazilian children.…”

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

“…The finding of only one typical EPEC strain was somewhat surprising, but appears to confirm a recent trend that has been observed in Brazil (Girão et al 2001, Da Silva Duque et al 2002, Rodrigues et al 2002. Until the 90s, these organisms were the main cause of infantile diarrhea in Brazil (Gomes et al 1991, Rosa et al 1998, ReguaMangia et al 2004), but it seems that they are becoming more and more rare.…”

Characterization of Atypical Enteropathogenic Escherichia coli Strains That Express Typical Localized Adherence in HeLa Cells in the Absence of the Bundle-Forming Pilus

“…However, recent studies in Brazil have shown a decrease in their isolation rates and an apparent increase in the frequency of aEPEC (9,17,18,21), but the role of the latter group in diarrhea has not been established. Since aEPEC strains show a very diverse repertoire of virulence genes, studies of subgroups of strains sharing specific properties might help in the identification of novel virulence factors and/or combinations of known virulence genes that could confirm their role as enteropathogens (10,22).…”