Enteropathogenicity markers in Escherichia coli isolated from infants with acute diarrhoea and healthy controls in Rio de Janeiro, Brazil

Abstract

BACTERIAL PATHOGENICITY AND CHARACTERISATIONEn t ero pat h og en i ci ty m a r kers i n Escrt erichia coli isolated from infants with acute diarrhoea and healthy controls in Rio de Janeiro, Brazil Sa'o Paulo, Brazil Faeces from urban children < 2 years old 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 Olll:H2, 055:NM and 01 19: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 FASf and eaeAf, 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 cellassociated 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.

Prevalence of diarrheagenic Escherichia coli in children with diarrhea in Salvador, Bahia, Brazil

“…In addition, we identified two EHEC/ STEC strains and observed a very low frequency of t-EPEC. The frequency of the remaining categories was similar to that reported in previous studies (Gomes et al 1991, Rosa et al 1998, Regua-Mangia et al 2004). Tornieporth et al (1995) conducted an epidemiological study with children in Salvador, Bahia.…”

“…Until the 90s, these organisms were the main cause of infantile diarrhea in Brazil (Gomes et al 1991, Rosa et al 1998, ReguaMangia et al 2004), but it seems that they are becoming more and more rare. The reason for this fall in the typical EPEC frequency has not been established but it may be a consequence of recent public health measures such as more efficient control of hospital infections and implementation of regular water supply in many slums.…”

Virulence Markers of Enteroaggregative Escherichia coli Isolated from Children and Adults with Diarrhea in Brasília, Brazil

“…Furthermore, Steiner et al (44) reported on an association of EAEC with growth impairment even in the absence of diarrheal symptoms. However, in some case-control investigations, EAEC strains were isolated at similar frequencies from patients with acute diarrhea and controls (15,16,35).The mechanisms by which these organisms cause diarrhea are not well understood; however, several virulence-related genes have been described. Most EAEC strains harbor a 60-to 65-MDa plasmid called pAA which has been shown to encode the aggregative adherence fimbriae AAF/I (28, 29, 40) and AAF/II (8); the enterotoxin EAST1, a toxin homologous to the heat-stable toxin (ST) of enterotoxigenic E. coli (38, 39); and Pet, a serine protease which has been described as causing enterotoxic and cytotoxic effects (30,31).…”

Epidemiology, Antimicrobial Resistance and &beta;-lactamase Genotypic Features of Enteropathogenic <i>Escherichia coli</i> Isolated from Children with Diarrhea in Southern China

“…The prevalence of EPEC has been reported as 16.3z, 2.7z, and 12.6z in Iran, Singapore, and Thailand, respectively (16)(17)(18). The reported prevalence of EPEC in children in Brazil ranges from 10.1 to 32.7z (19,20). EPEC is rarely reported in China, with only one previous study reporting a prevalence of 0.9z in Beijing (21).…”