Expression of membrane-associated proteins by strains of enteroaggregative Escherichia coli

Association between aggregative adherence fimbriae types including putative new variants and virulence-related genes and clump formation among aggR-positive Escherichia coli strains isolated in Thailand and Japan

Enteroaggregative Escherichia coli (EAggEC) are an important cause of diarrhea. Four types of AAF have been identified; however, their prevalence and association with virulence properties remain unclear. E. coli strains carrying the aggR gene as EAggEC that were isolated in Japan and Thailand (n = 90) were examined for AAF subunit genes, two toxin genes (pet/astA), and clump formation. The most prevalent AAF gene was hdaA (28%), followed by aafA (20%), aggA (12%), and agg3A (4%), as well as a putative new AAF sequence (25.6%). Retention status of the toxin genes and intensities of clump formation appeared to vary according to the AAF type.

A review of an emerging enteric pathogen: enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC) is an increasingly recognized enteric pathogen. It is a cause of both acute and persistent diarrhoea among children, adults and HIV-infected persons, in both developing and developed countries. In challenge studies, EAEC has caused diarrhoeal illness with the ingestion of 1010 c.f.u. Outbreaks of diarrhoeal illness due to EAEC have been reported, and linked to the ingestion of contaminated food. Diarrhoeal illness due to EAEC is the result of a complex pathogen–host interaction. Some infections due to EAEC result in diarrhoeal illness and elicit an inflammatory response, whereas other infections do not result in a symptomatic infection. Many putative virulence genes and EAEC strains that produce biofilm have been identified; however, the clinical significance of these genes and of biofilm production has yet to be defined. A −251 AA single nucleotide polymorphism (SNP) in the interleukin (IL)-8 promoter region is reported to increase host susceptibility to EAEC diarrhoea. Ciprofloxacin and rifaximin continue to be an effective treatment in persons infected with EAEC. This review is intended to provide an updated review for healthcare workers on EAEC, an emerging enteric pathogen.

Inhibition of enteroaggregative Escherichia coli adhesion to HEp-2 cells by secretory immunoglobulin A from human colostrum

BACKGROUND

Enteroaggregative Escherichia coli (EAEC) is an important agent of the persistent diarrhea among low socioeconomic level children in developing countries that may be associated with chronic undernourishment. Breast-feeding is effective in protecting infants against diarrhea and other infectious diseases. The aim of the study is to verify the ability of human colostrum to inhibit aggregative adhesion of EAEC to HEp-2 cells and the presence of antibodies reactive to antigenic fractions of EAEC in colostrum samples.

METHODS

Enzyme-linked immunosorbent assay, immunoblotting and adhesion assays of EAEC to HEp-2 cells were done with pooled or individual colostrum samples (n = 35). Assays were performed with a well-known EAEC strain, 044:H18 E. coli (strain 042). Colostral IgA was isolated by affinity chromatography in Sepharose anti-human alpha chain column.

RESULTS

Total colostrum and isolated IgA inhibited EAEC adhesion, and this ability was associated with the presence of IgA antibodies against a 15-kDa band, compatible with the subunits of aggregative adherence fimbrial adhesin II, characteristic of the 042 strain, absent in its plasmid-cured isogenic strain, that was used as control. Individual colostrum samples also inhibited adhesion, showed variable antibody titles against EAEC antigens in enzyme-linked immunosorbent assay and recognized many antigenic fractions in immunoblotting assays, including the 15-kDa band.

CONCLUSIONS

These results confirm that IgA from human colostrum inhibits adhesion of EAEC to HEp-2 cells and suggest that colostrum IgA antibodies reactive to EAEC antigens may play a role in protection of infants against diarrhea caused by these bacteria.