Adhesion of Diarrheagenic Escherichia coli and Inhibition by Glycocompounds Engaged in the Mucosal Innate Immunity.

Alex Pereira,Loreny Giugliano

doi:10.3390/biology2020810

Abstract

Escherichia coli colonizes the human intestine shortly after birth, with most strains engaging in a commensal relationship. However, some E. coli strains have evolved toward acquiring genetic traits associated with virulence. Currently, five categories of enteroadherent E. coli strains are well-recognized, and are classified in regard to expressed adhesins and the strategy used during the colonization. The high morbidity associated with diarrhea has motivated investigations focusing on E. coli adhesins, as well on factors that inhibit bacterial adherence. Breastfeeding has proved to be the most effective strategy for preventing diarrhea in children. Aside from the immunoglobulin content, glycocompounds and oligosaccharides in breast milk play a critical role in the innate immunity against diarrheagenic E. coli strains. This review summarizes the colonization factors and virulence strategies exploited by diarrheagenic E. coli strains, addressing the inhibitory effects that oligosaccharides and glycocompounds, such as lactoferrin and free secretory components, exert on the adherence and virulence of these strains. This review thus provides an overview of experimental data indicating that human milk glycocompounds are responsible for the universal protective effect of breastfeeding against diarrheagenic E. coli pathotypes.

Highlights

Escherichia coli colonizes the human intestine shortly after birth, with most strains engaging in a commensal relationship
In contrast to the type 1 pili, which were commonly harbored by commensal E. coli strains, fimbrial antigens colonization factor antigens (CFA) were characterized by mediating mannose-resistance hemagglutination (MRHA) [8,9]
Despite the fact that the protective factors in human milk had not been clearly identified, there was a strong belief that the protection involved, exclusively, anti-microbial factors such as the immunoglobulin content and, even, the presence of IgA-synthesizing lymphocytes in the human milk [103]

Summary

The Discovery of Diarrheagenic Categories of Escherichia coli

Escherichia coli is the predominant member of the Proteobacteria phylum and the dominant facultative anaerobe bacterium forming the gut microbiota [1]. Five enteroadherent E. coli pathotypes are well recognized These diarrheagenic categories are characterized by virtue of their harboring specific colonization factors, expressing different adhesion patterns on cultured cells, and carrying out different strategies in order to colonize and persist on mucosal surfaces of the gut (Table 1) [1,5]. Pathotypes of E. coli express specific adherence factors that allow the bacterial cells to explore eukaryotic cell receptors that commensal E. coli strains normally cannot do These colonization factors are diverse in structure and they can be seen as hair-like polymeric structures that extend beyond the bacterial surface such as fimbriae, fibriallae and pili; or they can be present as non-polymeric afimbrial adhesins [1,5]. Some adhesion factors can trigger signal transduction pathways what allows the bacteria to manipulate host cell functions during the pathogenesis [1,5]

Adhesins of Enterotoxigenic Escherichia coli

Findings

Conclusions