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Enterotoxigenic Escherichia coli (ETEC) strains are involved in piglet post-weaning diarrhea, a current problem in piglet rearing. Many prophylactic measures such as vaccines or feed additives such as probiotics have been tested in infection experiments with piglets [1-3]. In the present study, we tested if effects of ETEC can also be evoked when the strain is added in vitro to whole mucosal tissues which might represent a more complex model system compared to cell cultures. Furthermore it was examined if this response could be modulated by prior (in vivo) supplementation of the piglets with probiotics.
Material and methods: Jejunal epithelial tissues from piglets before weaning from a probiotic-supplemented (Enterococcus faecium NCIMB 10415) and a control group were taken and mounted into conventional Ussing chambers. The ETEC strain O149:K91:K88 was added at a concentration of 108 CFU/ml at the mucosal side of the tissues and barrier and immunological functions were examined by measuring electrophysiological parameters (transepithelial electrical resistance (Rt), potential difference and short circuit current (Isc)), as well as gene and protein expression of selected target genes by quantitative PCR and Western blots. Variance analyses and t-tests were performed
for statistical evaluation of the data.
Results: The Rt initially increased in the first two hours after ETEC addition, and decreased again later. The rise in Rt coincided with reduced fluorescein fluxes as a marker of paracellular permeability in the ETEC-incubated epithelia. At the end of the experiment mRNA expression of proinflammatory cytokines and of components of the inflammasome as a potential induction pathway were elevated. Expression of the tight junction protein claudin-4 was decreased in mucosal tissues treated with the pathogenic E. coli. Coherent effects of the probiotic prefeeding of the pigs could not be observed.
Conclusion: The in vitro system can be applied to study the early events of ETEC infection. Addition of ETEC affected barrier function and components of the gut immune system. Further studies are needed to elucidate the response under different incubation conditions.
This study was supported by German Research Foundation grant no. SFB 852/1 and LO 2058/1-1.