Factors associated with typical enteropathogenic Escherichia coli infection among children <5 years old with moderate-to-severe diarrhoea in rural western Kenya, 2008-2012

Designing of immunodiagnostic assay using polyclonal antibodies for detection of Enteropathogenic Escherichia coli strains

Enteropathogenic Escherichia coli (EPEC) is a significant bacterial pathogen that causes infantile diarrhea, particularly in low- and middle-income countries. The lack of a reliable diagnostic method greatly contributes to the increased occurrence and severity of the disease. This study aimed at developing of a cost-effective, rapid, and efficient immunodiagnostic assay for detecting EPEC infection. Lipopolysaccharide (LPS) was extracted from overnight EPEC cultures and combined with alum adjuvant, and then injected into mice for three rounds of immunizations. Subsequently, sera were collected after each immunization and utilized in agglutination assays conducted on glass slides. Both the LPS and colonies of the EPEC isolate used for LPS preparation were employed in these agglutination assays. To evaluate the assay's performance, a total of 34 bacteria, which comprise pathogenic, non-diarrheic E. coli and non-E. coli pathogenic bacteria were used. The developed assay detected EPEC, which yielded positive reactions within 6 minutes on average for both purified LPS and bacterial isolates. The assay exhibited 100% sensitivity and a 95.83% specificity for the detection of EPEC local isolates. Moreover, the assay also detected a low number of bacteria forming units (104X 104 CFU/ml) in spiked fecal samples. This study conclusively confirms that the developed immunodiagnostic assay possesses multiple favorable characteristics, including user-friendliness, high sensitivity, high specificity, cost-effectiveness, and time-efficiency. Hence, this assay can be used as ideal diagnostic assay, which is highly suitable for the detection and screening of EPEC infection in both humans and cattle in one health perspective of resource-limited laboratories.

Phenotypic diversity of type III secretion system activity in enteropathogenic Escherichia coli clinical isolates

Introduction. Enteropathogenic Escherichia coli (EPEC) strains pose a significant threat as a leading cause of severe childhood diarrhoea in developing nations. EPEC pathogenicity relies on the type III secretion system (T3SS) encoded by the locus of enterocyte effacement (LEE), facilitating the secretion and translocation of bacterial effector proteins.Gap Statement. While the regulatory roles of PerC (plasmid-encoded regulator) and GrlA (global regulator of LEE-activator) in ler expression and LEE gene activation are well-documented in the EPEC prototype strain E2348/69, understanding the variability in LEE gene expression control mechanisms among clinical EPEC isolates remains an area requiring further investigation.Aim. This study aims to explore the diversity in LEE gene expression control mechanisms among clinical EPEC isolates through a comparative analysis of secretion profiles under defined growth conditions favouring either PerC- or GrlA-mediated activation of LEE expression.Methodology. We compared T3SS-dependent secretion patterns and promoter expression in both typical EPEC (tEPEC) and atypical EPEC (aEPEC) clinical isolates under growth conditions favouring either PerC- or GrlA-mediated activation of LEE expression. Additionally, we conducted promoter reporter activity assays, quantitative real-time PCR and Western blot experiments to assess gene expression activity.Results. Significant differences in T3SS-dependent secretion were observed among tEPEC and aEPEC strains, independent of LEE sequence variations or T3SS gene functionality. Notably, a clinical tEPEC isolate exhibited increased secretion levels under repressive growth conditions and in the absence of both PerC and GrlA, implicating an alternative mechanism in the activation of Ler (LEE-encoded regulator) expression.Conclusion. Our findings indicate that uncharacterized LEE regulatory mechanisms contribute to phenotypic diversity among clinical EPEC isolates, though their impact on clinical outcomes remains unknown. This challenges the conventional understanding based on reference strains and highlights the need to investigate beyond established models to comprehensively elucidate EPEC pathogenesis.