<i>In vivo</i> colonization of <i>E. coli</i> commensal biofilm by enteroaggregative <i>E. coli</i> 55989 pathogen.

<p><b>A</b> Schematic representation of the experimental procedure. <b>B</b> Streptomycin-treated mice were first challenged intragastrically with commensal wild-type MG1655-s F′ (C) or its mutant Δ<i>yceP</i>, Δ<i>yliE</i>, and Δ<i>yiaF</i> derivatives (C*), followed on day 11 by administration of the <i>E. coli</i> 55989a-s pathogen. Numbers of commensal and pathogenic cfus recovered per gram of feces were determined every other day from day 3 to day 20. The lower limit of detection for bacteria was 10² cfu/g of feces. Box-and-whiskers plot indicates high and low values, median and interquartile ranges; each group contained between 8 and 12 mice. Pearson analysis of the bacterial count in faeces (impact of the initial colonization by the wild-type MG1655-s F′ or its derivatives on the capacity of the pathogen (Enteroaggregative <i>E. coli</i> 55989a-s) to colonize the mice intestine) and Mann-Whitney analysis of the number of the pathogen CFUs recovered (comparison of pathogen colonization level in mice precolonized with either MG1655-s F′ (control) or its derivatives (<i>yliE</i>, <i>yceP</i> or <i>yiaF</i>)) were performed. Statistically different results (P<0.05), are indicated by an asterisk.