Typical Enteroaggregative Escherichia coli Is the Most Prevalent Pathotype among E. coli Strains Causing Diarrhea in Mongolian Children

Abstract

Diarrhea remains one of the main sources of morbidity and mortality in the world, and a large proportion is caused by diarrheagenic Escherichia coli. In Mongolia, the epidemiology of diarrheagenic E. coli has not been well studied. A total of 238 E. coli strains from children with sporadic diarrhea and 278 E. coli strains from healthy children were examined by PCR for 10 virulence genes: enteropathogenic E. coli (EPEC) eae, tir, and bfpA; enterotoxigenic E. coli (ETEC) lt and st; enteroinvasive E. coli (EIEC) ipaH; enterohemorragic E. coli stx1 and stx2; and enteroaggregative E. coli (EAEC) aggR and astA. EAEC strains without AggR were identified by the HEp-2 cell adherence test. The detection of EAEC, ETEC, EPEC, and EIEC was significantly associated with diarrhea. The incidence of EAEC (15.1%), defined by either a molecular or a phenotypic assay, was higher in the diarrheal group than any other category (0 to 6.0%). The incidence of AggR-positive EAEC in the diarrheal group was significantly higher than in the control group (8.0 versus 1.4%; P ‫؍‬ 0.0004), while that of AggR-negative EAEC was not (7.1 versus 4.3%). Nineteen AggR-positive EAEC strains harbored other EAEC virulence genes-aggA, 2 (5.5%); aafA, 4 (11.1%); agg-3a, 5 (13.8%); aap, 8 (22.2%); aatA, 11 (30.5%); capU, 9 (25.0%); pet, 6 (16.6%); and set, 3 (8.3%)-and showed 15 genotypes. EAEC may be an important pathogen of sporadic diarrhea in Mongolian children. Genetic analysis showed the heterogeneity of EAEC but illustrated the importance of the AggR regulon (denoting typical EAEC) as a marker for virulent EAEC strains.Diarrhea continues to be one of the most common causes of morbidity and mortality among infants and children in developing countries (5, 18). Five distinct classes of diarrheagenic Escherichia coli (DEC) are recognized as being associated with diarrheal disease. They are enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), and enteroaggregative E. coli (EAEC); diffuse adhering E. coli (DAEC) may represent a sixth category, but this has not been clearly established (18). Each class of DEC is defined on the basis of distinct virulence characteristics, and tests for these characteristics have been developed to distinguish DEC classes from each other and from nonpathogenic E. coli strains of the normal flora (15, 34). The epidemiological significance of each E. coli category in childhood diarrhea varies with the geographical area. It has become clear that there are important regional differences in the prevalences of the different categories of DEC. The incidences of diarrheal illnesses caused by the different categories of DEC were examined mainly in Latin America, Africa, southern and Southeast Asia, and the Middle East (1,3,25,32,35,36,45). Study of the prevalences of DEC categories and their importance in childhood diarrhea has not been carried out in Mongolia. Therefore, to define the association of various categories of E. coli with diarrhea in Mongolia, w...

Enteroaggregative Escherichia coli in diarrheic children in Egypt: molecular characterization and antimicrobial susceptibility

“…A recent study from Libya found similar results, with multivirulence being detected in 50% of EAEC from diarrheic children [26]. Sarantuya et al reported a lower rate (< 30%) of multivirulence among EAEC from children with diarrhea in Mongolia [32].…”

Putative Virulence Genes and Biofilm Production Among Typical Enteroaggregative Escherichia coli Isolates from Diarrhoeic Children in Kashmir and Andhra Pradesh

“…In the present study 35.2 % isolates did not produce any quantifiable biofilm although all the strains were aggR positive. This corroborates with the findings of other workers [17,20] who also observed no correlation between aggR and biofilm formation. However, Mohamed et al [12] observed that isolates carrying aggR alone or in combination with other virulence genes were strongly associated with biofilm formation.…”

Molecular Characterization of Diarrheagenic Escherichia coli from Libya

“…47 We found three or more virulence genes (multivirulent isolates) in 50% of EAEC isolates. Sarantuya and others 48 reported multivirulence in 30% of EAEC from diarrheic children in Mongolia. A study from Brazil examined EAEC from diarrheic and control children for 11 virulence markers and found multivirulence in 74% of EAEC strains.…”

“…Results of this study show an abundance of typical rather than atypical EAEC among diarrheic Libyan children, as reported elsewhere. 47,48 Previous studies have reported that astA (EAST1) is not restricted to EAEC isolates and is significantly associated with diarrhea. 49,50 Furthermore it has been observed that, in addition to toxin EAST1, pet (Pet) seems to be common in the E. coli population and not restricted to EAEC.…”