Enteroadherent Escherichia coli and diarrhea in children: a prospective case-control study

Abstract

The relative contribution of diarrheagenic Escherichia coli was examined during a 1-year prospective study of hospitalized children in Clermont-Ferrand, France, including 220 case patients (with diarrhea) and 211 matched controls. Fecal isolates were characterized by means of their pattern of adherence to HEp-2 cells and by colony hybridization with DNA probes specific for the six categories of diarrheagenic E. coli. No enteroinvasive or enterotoxigenic E. coli isolates were isolated. Twenty-eight (6.5%) eae-positive isolates and 39 (9%) enteroaggregative E. coli isolates characterized with the aggregative adherence probe and/or by their adherence pattern were detected; they were equally distributed among the patients and the controls. Diffusely adhering E. coli was the predominant pathotype: 30.7% were detected by their adherence pattern and 13.7% were detected with the daaC probe. They were isolated with similar frequencies from the patients and the controls, thereby showing no association with diarrhea. However, daaC-positive strains were significantly associated with a past record of urinary tract infections. These results suggest that the diffusely adhering E. coli organisms isolated in the present study are not true intestinal pathogens but may be regarded as resident colonic strains. Escherichia coli strains associated with diarrheal disease have been divided into categories on the basis of pathogenic mechanisms. By using an assay measuring mannose-resistant bacterial adherence to the HEp-2 cell line, three pathotypes of E. coli have been distinguished so far (39). The localized adherence (LA) pattern refers to the formation of distinct microcolonies or bacterial clusters on the HEp-2 cell surface. This phenotype is characteristic of enteropathogenic E. coli (EPEC) responsible for infantile diarrhea in developing countries (9). The second pattern, called aggregative adherence (AA) refers to a pattern whereby bacteria adhere to each other and form a stacked brick-like lattice on the epithelial cells and on glass coverslips (39). Several epidemiological studies with infants and children in developing countries have noted an association between this adherence pattern and persistent diarrhea (6, 10, 52). The last group is referred to as diffusely adhering E. coli (DAEC). Many epidemiological studies concerning the involvement of this last group in infantile diarrhea have been conducted, but they led to contradictory results (2,

Pathogenesis of Afa/Dr Diffusely AdheringEscherichia coli

“…It is tempting to propose that Afa/Dr DAEC is a "silent pathogen" that can emerge from the human intestinal microbiota. Indeed, it is intriguing that epidemiological studies have revealed that Afa/Dr DAEC strains may be regarded as resident colonic strains, since daaC-positive E. coli strains have been isolated with similar frequencies from patients and control subjects (127,167,356). The resident luminal bacteria seem to be an important factor in the development and chronicity of inflammatory bowel diseases, and an aggressive immunological response may be triggered by these bacteria rather than as a result of a change in the normal flora (261).…”

“…The first DNA probe, named daaC, was generated by Stapleton et al (413) and was a 300-bp PstI fragment of plasmid pSSS1 (daa operon), coding for part of an accessory protein of F1845 adhesin expressed by the diarrheagenic Afa/Dr DAEC C1845 strain (43). This DNA probe has been used in a large majority of the epidemiological studies of the association of Afa/Dr DAEC with diarrhea and urinary tract infections (1,5,68,112,127,130,131,141,143,152,208,209,256,257,293,329,344,364,366,367,400). Another constructed DNA probe, named drb (130), was a 260-bp PstI fragment of plasmid pIL14 (afa-1 operon) coding for the AfaE-I adhesin expressed by the uropathogenic Afa/Dr DAEC KS52 strain (243).…”

“…Epidemiological studies conducted by use of colony blotting with the daaC DNA probe have demonstrated an age-related incidence of Afa/Dr DAEC in diarrhea in children, which apparently begins after age 2 or 3 (112,127,141,143,152,167,208,209,256,344,364). Moreover, E. coli strains expressing Afa/Dr adhesins have been found with similar frequencies in patients with diarrhea and control subjects (127,167,356). Recently Blanc-Potard et al (48), using representational difference analysis, have revealed that three sequences (MO30, S109, and S111) were specifically present in the wild-type, diarrhea-associated C1845 strain (43).…”

“…Moreover, E. coli expressing Dr adhesin has been shown to be associated with a twofold increase in the risk of a second UTI, suggesting its possible association with recurrent or chronic UTI (131). Forestier et al (127) found that daaC-positive strains were significantly associated with a past record of urinary tract infections. Zhang et al (470) screened UTI and fecal E. coli isolates for the presence of Dr sequences (drb) and found that among the drb-positive strains examined, 18% were afaE1 positive, 1.3% were afaE2 positive, 1.3% were afaE3 positive, 12% were draE positive, and 1.3% were daaE positive, whereas 12% were draE-afaE3 hybrid.…”

“…A retrospective case-control study has shown that among children suffering from gastroenteritis in whom DAEC was present, those who were daaC positive spent significantly longer in the hospital than those who were daaC negative (344). A 1-year prospective study of hospitalized children in France, including 220 patients with diarrhea and 211 matched controls, showed that Afa/Dr DAEC was the predominant pathotype, since 30.7% were detected by their adherence pattern and 13.7% were detected with the daaC probe (127). The clinical significance of E. coli in children with diarrhea in New Caledonia has been investigated (141).…”