Enteropathogenicity markers in Escherichia coli isolated from infants with acute diarrhoea and healthy controls in Rio de Janeiro, Brazil
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1998-09-01
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Gomes, Tania Aparecida Tardelli 
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Faeces from urban children <2 years aid with acute diarrhoeal illness and from nondiarrhoeal infants (controls) were examined for Escherichia coli and other enteropathogens, A total of 990 E, coli isolates from 100 patients and 50 controls was tested for enteropathogenic E, coli (EPEC) serotype (O:H), adherence to HEp-2 cells after incubation for 3 and 6 h, fluorescent actin staining (FAS), DNA hybridisation with EAF, eaeA, STh, STp and EAggEC probes and production of heat-labile enterotoxin (LT) and verocytotoxin (VT) with Y1 and Vero cells, EPEC were the most prevalent enteropathogens in patients (32.7%; and 14% in controls), Enteroinvasive E, coli (EIEC) and Vero cytotoxin-producing E, coli (VTEC) were not detected, The rate of isolation of enterotoxigenic E, coli (ETEC) was identical in both groups, Among the EPEC isolates the prevalent serotypes were O111:H2, O55:NM and O119:H6, Localised adherence (LA) was found significantly more frequently in isolates from patients (19.6%) than controls (2.1%), All LA-positive EPEC isolates were FAS+ and eaeA+, but only 75.2% of them hybridised with the EAF probe. Diffusely adhering E, coli (DAEC) and enteroaggregative E, coli (EAggEC) mere found with equal frequency in patients and controls, Twenty-seven E, coli isolates were negative far EAF but positive for eaeA and FAS and produced LA in 6-h adherence tests, These EAF(-)/eaeA+ strains were the only putative enteropathogen identified in seven patients and were not found in controls, The ability of these strains to elicit ultrastructural cell alterations and cell-signalling events was evaluated in Caco-2 cells (human colon carcinoma cell line) by the gentamicin invasion assay and by transmission electron microscopy, The numbers of intracellular bacteria in cell invasion tests varied from 0.4% to 1.6% of the cell-associated bacteria after a 6-h incubation period, Tyrosine phosphorylation of host cell proteins was assessed in HEp-2 cells by immunofluorescence microscopy and all strains gave positive results, EAF-/eaeA+ E, coli strains express most of the virulence properties found among true EPEC strains and can be a relevant cause of infant diarrhoea in developing countries.
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Journal Of Medical Microbiology. Philadelphia: Lippincott Williams & Wilkins, v. 47, n. 9, p. 781-790, 1998.