Abstract
BackgroundDiffusely adherent Escherichia coli (DAEC) have been considered a diarrheagenic category of E. coli for which several potential virulence factors have been described in the last few years. Despite this, epidemiological studies involving DAEC have shown inconsistent results. In this work, two different collections of DAEC possessing Afa/Dr genes, from children and adults, were studied regarding characteristics potentially associated to virulence.ResultsDAEC strains were recovered in similar frequencies from diarrheic and asymptomatic children, and more frequently from adults with diarrhea (P < 0.01) than from asymptomatic adults. Association with diarrhea (P < 0.05) was found for SAT-positive strains recovered from children and for curli-positive strains recovered from adults. Mixed biofilms involving DAEC and a Citrobacter freundii strain have shown an improved ability to form biofilms in relation to the monocultures. Control strains have shown a greater diversity of Afa/Dr adhesins and higher frequencies of cellulose, TTSS, biofilm formation and induction of IL-8 secretion than strains from cases of diarrhea in children.ConclusionsDAEC strains possessing Afa/Dr genes isolated from children and adults represent two different bacterial populations. DAEC strains carrying genes associated to virulence can be found as part of the normal microbiota present in asymptomatic children.
Highlights
Adherent Escherichia coli (DAEC) have been considered a diarrheagenic category of E. coli for which several potential virulence factors have been described in the last few years
Prevalence of Diffusely adherent Escherichia coli (DAEC) strains A total of 1,253 E. coli isolates recovered from stool samples of 127 cases of diarrhea in children and 127 asymptomatic controls were examined for the presence of genes belonging to the conserved region of the afa operons, which encode the Afa/Dr family of adhesins
Characteristics potentially associated to virulence are distinct in DAEC strains from adults and children
Summary
Adherent Escherichia coli (DAEC) have been considered a diarrheagenic category of E. coli for which several potential virulence factors have been described in the last few years. Two different collections of DAEC possessing Afa/Dr genes, from children and adults, were studied regarding characteristics potentially associated to virulence. Characterization of truly diarrheagenic groups or strains can be a complex task because this species is one of the first colonizers of the human gut. Adherent Escherichia coli have been considered a diarrheagenic group of E. coli (DEC). They are characterized by the diffuse adherence pattern on cultured epithelial cells HeLa or HEp-2 [2]. Since Germani et al [4] demonstrated that, among DAEC strains, only those that were positive to daaC probe - that recognize a conserved region from Afa/Dr adhesins operons - were found in
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