Related Experiment Videos
Virulence properties of atypical EPEC strains
J S Pelayo, I C A Scaletsky1, M Z Pedroso1
1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo/Escola Paulista de Medicina, 04023-062 São Paulo, Brazil.
Abstract:
Virulence properties of 31 atypical enteropathogenic Escherichia coli (EPEC) strains isolated from cases of diarrhoea were examined. All except two strains adhered to HEp-2 cells in a localised adherence-like (LAL) pattern. With the exception of two strains, all were fluorescent actin staining (FAS) positive. Gentamicin HEp-2 invasion assay studies showed that all strains were invasive. Transmission electron microscopy of infected HEp-2 cells showed the characteristic attaching and effacing lesion and invasion of the cultured cells. Of the nine strains that hybridised with a DNA probe for alpha-haemolysin, five were haemolytic within 3 h of incubation, while the remaining strains were haemolytic only after incubation for 24 h. Three strains produced enterohaemolysin on blood agar. None of the 31 strains of E. coli induced fluid accumulation in the rabbit intestinal loop assay or displayed cytotoxic effects in HeLa and Vero cells. All the strains belonging to serotypes O26:H11, O26:H- and 0119:H2 expressed intimin beta, whereas all the strains from serotype O55:H7 expressed intimin gamma. The strains belonging to serogroup O111 expressed a non-typable intimin. The participation of intimin in LAL was supported by adhesion inhibition experiments in which antibodies to intimin significantly reduced the level of LAL.
Insights
Atypical enteropathogenic Escherichia coli (EPEC) strains causing diarrhea exhibit localized adherence and invasiveness. Intimin, a key virulence factor, plays a significant role in EPEC
Area of Science:
- Microbiology
- Pathogen Research
- Molecular Biology
Background:
- Atypical enteropathogenic Escherichia coli (EPEC) are significant causes of diarrheal disease.
- Understanding EPEC virulence factors is crucial for disease control.
Purpose of the Study:
- To characterize the virulence properties of atypical EPEC strains isolated from human diarrheal cases.
- To investigate the role of intimin in EPEC adherence and pathogenicity.
Main Methods:
- HEp-2 cell adherence assays (localized adherence-like pattern)
- Fluorescent actin staining (FAS)
- Gentamicin invasion assays
- Transmission electron microscopy (TEM)
- DNA hybridization for alpha-haemolysin
- Rabbit intestinal loop assay
- HeLa and Vero cell cytotoxicity assays
- Intimin typing (serotypes O26, O119, O55, O111)
- Adhesion inhibition experiments with anti-intimin antibodies
Main Results:
- 31 atypical EPEC strains showed localized adherence-like pattern and invasiveness in HEp-2 cells.
- Characteristic attaching and effacing lesions were observed via TEM.
- Nine strains hybridized with an alpha-haemolysin probe, with varying hemolytic activity.
- No strains induced fluid accumulation or showed cytotoxicity in relevant assays.
- Specific intimin types (beta, gamma, non-typable) were associated with different EPEC serotypes.
- Antibodies to intimin significantly reduced localized adherence-like pattern, confirming its role.
Conclusions:
- Atypical EPEC strains possess key virulence factors including adherence and invasiveness.
- Intimin is a critical determinant of localized adherence in these EPEC strains.
- Further research into atypical EPEC pathogenesis is warranted.