Enteropathogenic Escherichia coli (EPEC) expressing a non-functional bundle-forming pili (BFP) also leads to increased growth failure and intestinal inflammation in C57BL/6 mice

Abstract

Bundle-forming pili (BFP) are implicated in the virulence of typical enteropathogenic E. coli (EPEC), resulting in enhanced colonization and mild to severe disease outcomes; hence, non-functional BFP may have a major influence on disease outcomes in vivo. Weaned antibiotic pre-treated C57BL/6 mice were orally infected with EPEC strain UMD901 (E2348/69 bfpA C129S); mice were monitored daily for body weight; stool specimens were collected daily; and intestinal tissues were collected at the termination of the experiment on day 3 post-infection. Real-time PCR was used to quantify fecal shedding and tissue burden. Intestinal inflammatory biomarkers lipocalin-2 (LCN-2) and myeloperoxidase (MPO) were also assessed. Infection caused substantial body weight loss, bloody diarrhea, and intestinal colonization with fecal and intestinal tissue inflammatory biomarkers that were comparable to those previously published with the wild-type typical EPEC strain. Here we further report on the evaluation of an EPEC infection model, showing how disruption of bfp function does not impair, and may even worsen diarrhea, colonization, and intestinal disruption and inflammation. More research is needed to understand the role of bfp in pathogenicity of EPEC infections in vivo.

Keywords: Bundle-forming pili; Diarrhea; Enteropathogenic E. coli; Inflammation; Murine model.

Fig. 1

UMD901 (non-functional BFP) affects weight gain, bloody stools accompanied with increased shedding and tissue burden in C57BL/6 mice. A Weaned mice pre-treated with antibiotic cocktail were infected with WT EPEC and UMD901; monitored daily for changes in weight (n = 12/group). #p = 0.003 and &p = 0.0004, data analyzed using two-way ANOVA and Turkey’s post hoc test. B Change in stool appearance of uninfected and infected (WT and/or UMD901 EPEC) mice. C Stool shedding of strain UMD901 vs WT EPEC infected mice. D Colonization of WT and UMD901 in different intestinal tissue sections at day 3 p.i. (n = 8/group) The uninfected and WT EPEC data has already been published [24] and are included here for comparison with the simultaneously studied strain UMD901 infected mice that are first reported herein

Fig. 2

Infection of strain UMD901 in mice causes increased inflammatory biomarkers. A Fecal inflammatory biomarkers MPO (n = 8 uninfected and WT, 9 UMD901/group) and LCN-2 (n = 6 uninfected and UMD901, 5 WT/group) measured in stool specimens collected at day 2 p.i. B Inflammatory biomarkers MPO (n = 4 uninfected, 7 WT, 8 UMD901/group) and LCN-2 (n = 4/group) measured from cecal contents of mice collected at day 3 p.i. Data analyzed using Kruskal–Wallis and Dunn’s multiple comparison test *p = 0.03, #p = 0.003, &p = 0.0009. As noted in the text, the WT EPEC data has already been published [24], but are included here for comparison with the simultaneously studied strain UMD901-infected mice that are first reported herein