Diarrheagenic Escherichia coli categories among the traditional enteropathogenic E. coli O serogroups: a review

Abstract

The species Escherichia coli is serologically divided in serogroups and serotypes on the basis of its antigenic composition (somatic or O antigens for serogroups and flagelar or H antigens for serotypes). Many strains express a third class of antigens (capsular or K antigens) that although important in pathogenesis only occasionally are used in serotyping.The species comprise intestinal and extraintestinal pathogens. The intestinal pathogens are also known as diarrheagenic E. coli (DEC) of which six categories have been characterized: enteropathogenic E. coli (EPEC), enterohaemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC), and diffusely adhering E. coli (DAEC) (Nataro & Kaper 1998). Recently EPEC has been divided in typical EPEC (t-EPEC) and atypical EPEC (a-EPEC) . There are many differences between these categories but in routine they are defined by a few virulence markers (Table I). The extraintestinal pathogens (EXPEC) more frequent includes the strains associated with urinary tract infections (UPEC), neonatal meningitis (MAEC), and bacteremia. For an excellent review on DEC see Nataro and Kaper (1998) and on E. coli in general Gyles (1994). E. coli is also a very important veterinary pathogen (Gyles 1994 (WHO 1987). At this time already there were studies showing that at least some of these serogroups contained different diarrheagenic serotypes but their pathogenic diversity only latter became really clear (Nataro & Kaper 1998).During the last 10 years we have studied most of the EPEC O serogroups in regard to DEC categories, serotypes, clones, and genetic relationships. The purpose of this article is to review these characteristics. It is based on the study of 805 strains of serogroups O26, O55, O86, O111, O114, O119, O125, O126, O127, O128, and O142 most of which were isolated in São Paulo from children with diarrhea between 1970 and 1990. All strains were studied in regard to adhesion patterns, virulence genes implicated in the definition of the DEC category, and serotypes. The strains of serogropus O55, O111, and O119 were also studied by MLEE and a representative number of strains of serogroups O86, O127, O128, and O142 were studied by ribotyping. Serogroup O26 was studied by RAPD. Potential virulence factors were studied in a representative number of strains of the DEC categories detected (Campos et al. 1994, Valle et al. 1997, Gonçalves et al. 1997, Monteiro-Neto et al. 1997, Dias 1998, Valle 1998, Ghilardi et al. 2003. Other studies performed will be mentioned during the review. DEC CATEGORIES IN THE EPEC O SEROGROUPSThe DEC categories and the number of strains of each category as well the number of avirulent strains are shown in Table II. Typical EPEC was the most frequent category followed by EAEC, atypical EPEC, ETEC, and EHEC. EIEC and DAEC were not found among the strains tested. A number of strains showed the diffuse adherence (DA) pattern but they proved to belong to the ETEC, EAEC, and atypical EPEC categories. The n...

Diarrheagenic Escherichia coli in sub-Saharan Africa: Status, Uncertainties and Necessities

“…Most other recommendations concur [174]. In addition to outbreaks, sporadic EHEC isolates have almost always been found when sought in Africa [14,21,65,89,133,143,172,[175][176][177]. Although the isolation rate was low in all these instances, they further emphasize the importance of considering EHEC in the differential diagnosis of bloody diarrhea.…”

“…ETEC is also a major etiologic agent of infantile diarrhea in African countries, which could benefit considerably from vaccine development [66,88]. Among children less than five years of age, ETEC is strongly associated with disease and in many studies was the most common cause of acute diarrhea [65,66,80,89]. ETEC can quickly produce potentially fatal dehydration in young children and has been associated with life-threatening persistent diarrhea in those who are malnourished [86,90].…”

Genetic relationship of diarrheagenic Escherichia coli pathotypes among the enteropathogenic Escherichia coli O serogroup

“…It was initially accepted that these serogroups comprised only EPEC and due to this belief these organisms were routinely identified by their O antigens only. Studies initiated in the early 1990s, and over the following years, revealed that the EPEC O serogroups would contain not only EPEC but also enterohemorrhagic E. coli (EHEC) and enteroaggregative E. coli (EAEC) (Campos et al 1994, Rodrigues et al 1996, Scotland et al 1996, Valle et al 1997, Gonçalves et al 1997, Trabulsi et al 2002, Ghilardi et al 2003, Campos et al 2004. It was further verified that there were two classes of EPEC: one harboring the EPEC adherence factor (EAF) plasmid and the other without this plasmid.…”

“…The first class was designated typical EPEC and the second atypical EPEC (Kaper 1996, Trabulsi et al 2002. It is now well established that the EPEC O serogroups contain EPEC (typical and atypical), EHEC and EAEC, and also that the four pathotypes are characterized by distinct serotypes (Campos et al 2004). …”

Caracterização genotípica e fenotípica de mutantes não aderentes de Escherichia coli enteropatogênica atípica do sorotipo O125ac:H6.

“…São esses sorogrupos: O26, O55, O86, O111, O114, O119, O125, O126, O127, O128, O142 e O158 (WHO, 1987). Entretanto, essa metodologia pode levar à detecção de outros patótipos de DEC, uma vez que alguns desses sorogrupos são constituídos por sorotipos que correspondem a outros patótipos de DEC CAMPOS et al, 2004). A detecção por métodos moleculares ou imunológicos dos genes de virulência, ou dos seus produtos, envolvidos no estabelecimento da lesão A/E também pode ser empregada (NATARO, 1996).…”