Escherichia coli strains involved in diarrhea in France: high prevalence and heterogeneity of diffusely adhering strains

Abstract

Two hundred sixty-two strains of Escherichia coli isolated from diarrheal stool specimens from infants, children, and adults hospitalized in Clermont-Ferrand, France, were studied to classify them in the previously described pathogenic groups of E. coli involved in diarrheal diseases. A total of 1.5% of them belonged to the enterotoxigenic E. coli pathotype, but none belonged to the enteroinvasive E. coli, enterohemorrhagic E. coli, or enteropathogenic E. coli pathotypes. Seventeen strains (6.5%) exhibited an aggregative pattern of adhesion to HEp-2 cells (EAggEC pathotype), but of these, three (17.6%) did not hybridize with the EAggEC DNA probe. Most of the strains involved in diarrhea belonged to the diffusely adhering E. coli group; 100 strains (38.2%) exhibited a diffuse adhesion (DA) to HEp-2 cells. Only eight strains (8.9%o) from controls diffusely adhered to HEp-2 cells. The highly significant difference (P < 0.0001) between DA strains from patients and from controls suggests that the diffusely adhering E. coli strains should be considered pathogens. Only 33 of them (33%) hybridized with the previously described DA DNA probe, and only 2 (2%) hybridized with the AIDA DNA probe. Four different major proteins were observed in the bacterial surface extracts of the 33 strains positive with the DA DNA probe. In addition, 16 strains that diffusely adhered to HEp-2 cells induced a cytotoxic effect on HEp-2 cells that was characterized by pyknosis and lysis of the cytoplasmic membrane. This cytotoxic effect was correlated with the synthesis of a hemolysin. The genes involved in diffuse adhesion to HEp-2 cells were located on conjugative R plasmids in strains that did not hybridize with the DA or AIDA * Corresponding author.

Pathogenesis of Afa/Dr Diffusely AdheringEscherichia coli

“…By way of comparison, the other pathogenic E. coli groups were only weakly represented: 0.6% of ETEC, 0.6% of EHEC, and 3.9% of EAEC. Neither EPEC or enteroinvasive E. coli was isolated during the study period (208,209). Importantly, an age-related incidence of Afa/Dr DAEC in diarrhea has been demonstrated.…”

“…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).…”

“…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. It is noteworthy that daaC-positive E. coli isolates from human patients with disease have been found that express other virulence factors, including aerobactin (130,441), the CS31A antigen reported for septicemic and bovine ETEC strains (207), cytotoxic necrotizing factor (130,131,212,441), and hemolysin (92,93,130,131,165,176,209,312,441). Recent data indicate that AfaE-1, AfaE-III, and F1845 adhesins are found in isolates from both human diarrhea and UTI (252).…”

Pathogenesis of Human Diffusely Adhering Escherichia coli Expressing Afa/Dr Adhesins (Afa/Dr DAEC): Current Insights and Future Challenges

“…However, the relationship between Afa/Dr DAEC and diarrhea in children as a function of age has been more convincingly demonstrated in age cross-sectional studies showing an increased incidence in children Ͻ1 to 5 years of age. These studies were conducted in the United States (116), Mexico (117), and different South American countries, including Chile (118), Brazil (58,71,(119)(120)(121), Colombia (122), Peru (123)(124)(125)(126)(127), and Argentina (128), as well as in Thailand (50), Bangladesh (129), Japan (119), New Caledonia (45,63,130), various places in Africa (131)(132)(133), and European countries, includ-ing the United Kingdom (134) and France (135,136). In Afa/Dr DAEC strains isolated from stools of children, the sat gene has been found in almost half of the diarrhea-associated Afa/DrDAEC strains and was not present in all the non-diarrhea-associated Afa/ DrDAEC strains (137).…”