Influência da limitação de ferro nas propriedades adesivas e na formação de biofilme de Escherichia coli enteroagregativa (EAEC)

Abstract

Escherichia coli enteroaggregative (EAEC) can cause persistent or acute diarrhea. It is characterized by the aggregative adherence pattern on HEp-2 cells, with the presence of bacteria aggregates like stacked bricks. Many strains have the capacity to produce siderophores, low-molecular-mass compounds that capture iron under conditions of low concentration of this element. The iron is an essential microelement to bacteria, because is used as cofactor of enzymes involved at importants cellular processes. Mareover, the iron can participate of reactive oxygen species production (ERO) by Fenton reaction. At this study, we analyzed the effects of low iron availability mediated by the chelator 2,2-dypiridyl at adhesives properties and biofilm formation of prototype EAEC 042 strain and EAEC clinical isolates. All strains showed a decreased adherence to HEp-2 and T84 cells under iron restriction, suggesting that iron homeostasis is important to adherence, the first step of EAEC pathogenesis. Besides, filament growth was observed at this condition. The study of biofilm formation revealed differences among the prototype EAEC 042 strain and the clinical isolates. While the prototype strain showed a decreased biofilm formation when under iron restriction, the clinical isolates showed an increase of this process. The capacity of thiourea, a hydroxyl radical scavenger, to revert the effects of iron restriction, suggests the occurrence of oxidative stress at the chelator presence. Our data show that iron homeostasis is important not only to bacterial growth, but also for protection against oxidative stress, a condition that also can occur in vivo, during the establishment of infections, through the action of neutrophiles and activated macrophages.