Enteropathogenicity markers in Escherichia coli isolated from infants with acute diarrhoea and healthy controls in Rio de Janeiro, Brazil.
Faeces from urban children < 2 years old with acute diarrhoeal illness and from non-diarrhoeal 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) were found with equal frequency in patients and controls. Twenty-seven E. coli isolates were negative for 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.
Rosa
A C
AC
Departamento de Microbiologia e Imunologia, Universidade do Estado do Rio de Janeiro, Brazil.
Mariano
A T
AT
Pereira
A M
AM
Tibana
A
A
Gomes
T A
TA
Andrade
J R
JR
D000208:Acute Disease; D000372:Agglutination Tests; D001422:Bacterial Adhesion; D001427:Bacterial Toxins / Q000096:biosynthesis; D001938:Brazil / Q000453:epidemiology; D018938:Caco-2 Cells; D002460:Cell Line; D003603:Cytotoxins / Q000096:biosynthesis; D015342:DNA Probes; D003968:Diarrhea, Infantile / Q000453:epidemiology / Q000382:microbiology*; D004768:Enterotoxins / Q000096:biosynthesis; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D029968:Escherichia coli Proteins; D005243:Feces / Q000382:microbiology; D006801:Humans; D015994:Incidence; D007223:Infant; D009693:Nucleic Acid Hybridization; D015995:Prevalence; D012703:Serotyping; D022622:Shiga Toxin 1; D014505:Urban Population; D014774:Virulence
D001427:Bacterial Toxins; D003603:Cytotoxins; D015342:DNA Probes; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D022622:Shiga Toxin 1; C027538:heat-labile enterotoxin, E coli