RESUMEN
Enteroinvasive Escherichia coli (EIEC) and Shigella spp cause bacillary dysentery in humans by invading and multiplying within epithelial cells of the colonic mucosa. Although EIEC and Shigella share many genetic and biochemical similarities, the illness caused by Shigella is more severe. Thus, genomic and structure-function molecular studies on the biological interactions of these invasive enterobacteria with eukaryotic cells have focused on Shigella rather than EIEC. Here we comparatively studied the interactions of EIEC and of Shigella flexneri with cultured J774 macrophage-like cells. We evaluated several phenotypes: (i) bacterial escape from macrophages after phagocytosis, (ii) macrophage death induced by EIEC and S. flexneri, (iii) macrophage cytokine expression in response to infection and (iv) expression of plasmidial (pINV) virulence genes. The results showed that S. flexneri caused macrophage killing earlier and more intensely than EIEC. Both pathogens induced significant macrophage production of TNF, IL-1 and IL-10 after 7 h of infection. Transcription levels of the gene invasion plasmid antigen-C were lower in EIEC than in S. flexneri throughout the course of the infection; this could explain the diminished virulence of EIEC compared to S. flexneri.
Asunto(s)
Citocinas/análisis , Escherichia coli/patogenicidad , Regulación Bacteriana de la Expresión Génica/inmunología , Macrófagos/microbiología , Shigella flexneri/patogenicidad , Factores de Virulencia/biosíntesis , Muerte Celular , Ensayo de Immunospot Ligado a Enzimas , Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica/genética , Genes Bacterianos , Humanos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Shigella flexneri/genética , Factores de Virulencia/genéticaRESUMEN
Non-motile enteroinvasive Escherichia coli (EIEC) is serotyped based only on O antigen polymorphism, since H antigen epitopes, present on the flagellins, cannot be characterised in these bacteria. In this study, we demonstrate the presence of the flagellin-coding fliC gene in non-motile EIEC strains. Moreover, we were able to group the 11 most common non-motile EIEC serotypes into six different RFLP patterns of the fliC gene. Amplicons representing each RFLP pattern were sequenced. Sequencing data were used to construct a phylogenetic tree which showed two main clusters: one sharing similarity with Shigella dysenteriae and pathogenic E. coli, and the other being closer to non-pathogenic E. coli.
Asunto(s)
Diarrea/microbiología , Escherichia coli/clasificación , Escherichia coli/genética , Flagelina/genética , Filogenia , Técnicas de Tipificación Bacteriana , Desoxirribonucleasas de Localización Especificada Tipo II , Diarrea/epidemiología , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Flagelina/metabolismo , Humanos , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , SerotipificaciónRESUMEN
We report that enteroinvasive Escherichia coli (EIEC) serotypes considered to be nonmotile produce an unusually large (77 kDa) flagellin that is assembled into functional flagellum filaments that allow the bacteria to swim in modified motility agar. The EIEC flagellin showed N-terminal identity to most common enterobacterial flagellins, especially those of the E. coli H7 serotype. These data are important in terms of the epidemiology, evolution, and biology of EIEC.