Typical and Atypical EnteropathogenicEscherichia coli

Abstract

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.

Escherichia coli virulence factors

“…Non BFP-producing EPEC from humans and animals are called atypical (a) EPEC (Nataro and Kaper, 1998;Trabulsi et al, 2002;Kaper et al, 2004;Hernandes et al, 2009). The BFP, that are encoded by plasmid-located genes, were at first thought to be involved in adherence to the human enterocytes, but are today believed to help bacteria to stick together forming micro-colonies at the surface of the host cells, also called "Localized Adherence" (LA) pattern (Scaletsky et al, 1984;Nataro and Kaper, 1998;Kaper et al, 2004).…”

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

“…This suggests that gain or loss of virulence elements, like phage (STX), plasmids (EHEC, EAF) and pathogenic islands (LEE), occurred in parallel among diarrheagenic E. coli strains. Moreover, the capacity of some EPEC and atypical EPEC strains for expressing potential virulence factors is not encoded in the LEE region (Trabulsi et al 2002), like EAST1 (heat-stable toxin 1 of EAEC), CDT (cytolethal distending toxin) and E-hly (EHEC hemolysin), suggesting again that these virulence elements are transferred horizontally and in parallel among different strains. It is interesting to note that strains belonging to the same pathotype isolated in different countries grouped toghether suggesting one more time the parallel transference of virulence factors.…”

“…Regarding virulence factors, EPEC, atypical EPEC, EHEC strains possess distinct intimins (α, β, γ and δ) and different insertion regions (selC ou pheU) for LEE, or Locus of Enterocyte Effacement (Adu-Bobie et al 1998, Sperandio et al 1998, Trabulsi et al 2002. This suggests that gain or loss of virulence elements, like phage (STX), plasmids (EHEC, EAF) and pathogenic islands (LEE), occurred in parallel among diarrheagenic E. coli strains.…”

“…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.…”

“…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).…”