Genotypic and Phenotypic Characterisation of Enteroaggregative Escherichia coli from Children in Rio de Janeiro, Brazil

Abstract

Enteroaggregative Escherichia coli (EAEC) is a significant cause of diarrhoeal illness in both children and adults. Genetic heterogeneity and recovery of EAEC strains from both healthy and diseased individuals complicates our understanding of EAEC pathogenesis. We wished to establish if genetic or phenotypic attributes could be used to distinguish between strains asymptomatically colonising healthy individuals and those which cause disease. Genotypic screening of a collection of twenty four EAEC isolates from children with and without diarrhoea revealed no significant differences in the repertoire of putative virulence factors present in either group of strains. In contrast, EAEC strains from phylogroup A were more strongly associated with asymptomatic groups whereas strains from phylogroup D were more associated with cases of diarrhoea. Phenotypic screening revealed no differences in the ability of strains from either cohort of children to form biofilms, to adhere to and invade cells in tissue culture or to cause disease in the Caenorhabditis elegans model of infection. However, the latter assay did reveal significant reduction in nematode killing rates when specific virulence factors were deleted from human pathogenic strains. Our results suggest that current models of infection are not useful for distinguishing avirulent from pathogenic strains of EAEC but can be useful in studying the effect of specific virulence factors.

Expression of different bacterial cytotoxins is controlled by two global transcription factors, CRP and Fis, that co-operate in a shared-recruitment mechanism

“…However, the expression of pet, sat and sigA is regulated by two global transcription factors that reflect the homoeostasis of the cell, suggesting that maximal expression occurs when it is physiologically suitable to mount an attack. As well as being an enterotoxin and cytopathic to human epithelial cells, Pet enhances killing of the nematode Caenorhabditis elegans, reflecting the toxin's virulence in very different systems [5,8]. As well as being an enterotoxin and cytopathic to human epithelial cells, Pet enhances killing of the nematode Caenorhabditis elegans, reflecting the toxin's virulence in very different systems [5,8].…”

“…The plasmid-encoded toxin (Pet) from EAEC strain 042 is a cytotoxic autotransporter protein that is secreted during EAEC infection [5,6]. Pet is encoded on a large virulence plasmid, pAA2, and it is an important virulence determinant for EAEC strain 042 [6][7][8]. It functions as a serine protease, which, once internalized by gut epithelial cells, leads to cleavage of the cytoskeletal component fodrin and results in cell rounding and detachment [6,9].…”

Ex Vivo Model of Rabbit Intestinal Epithelium Applied to the Study of Colonization by Enteroaggregative Escherichia Coli

“…As a negative control, non-infected intestinal fragments were used. The EAEC strains were previously characterised by DNA hybridization probe (3) or by polymerase chain reaction (PCR) (21) for putative virulence factors of EAEC (7,20) . Adhesion assays in intestinal cell lines after 6 hours of incubation was used to characterize the aggregative pattern (Table 1).…”

Mecanismos de virulencia de Escherichia coli enteropatógena

“…Este patotipo se adhiere a la mucosa intestinal, la coloniza y produce un efecto citotóxico que causa diarrea de tipo acuosa sin fiebre, con secreción de moco 84,85 . Entre las cepas de ECEA existe gran variabilidad en la presencia de factores de patogenicidad; por consiguiente, en los modelos estudiados aún no se ha encontrado relación entre un genotipo o fenotipo específico y el desarrollo de la enfermedad.…”

“…Entre las cepas de ECEA existe gran variabilidad en la presencia de factores de patogenicidad; por consiguiente, en los modelos estudiados aún no se ha encontrado relación entre un genotipo o fenotipo específico y el desarrollo de la enfermedad. Sin embargo, un estudio reciente describe la asociación entre las cepas ECEA y el grupo filogenético D, principalmente en pacientes sintomáticos 84 .…”