I-FABP, Pig-MAP and TNF-α as biomarkers for monitoring gut-wall integrity in front of Salmonella Typhimurium and ETEC K88 infection in a weaned piglet model

Having sensitive serum biomarkers able to determine the structural changes of the small intestine suffering from bacterial digestive diseases could be a valuable tool particularly in piglets at weaning, when intestinal infections are highly prevalent. We evaluated the usefulness of three inflammatory and gut-wall-integrity biomarkers to assess the degree of intestinal histo-morphological damage in piglets. Piglets were orally challenged with Salmonella Typhimurium or enterotoxigenic Escherichia coli (ETEC) to get a variable range of response according to individual variability. Forty-eight piglets were challenged with Salmonella Typhimurium and seventy-two with enterotoxigenic Escherichia coli K88. Clinical signs and faecal score were recorded. At Days 4 and 8 post-inoculation, blood was sampled, animals euthanised and distal ileum dissected. Morphological measures were obtained from the gut tissue, and serum tumour necrosis factor-alpha (TNF-α), pig major acute-phase protein (Pig-MAP) and intestinal fatty acid-binding protein (I-FABP) were determined. Animals developed mild-to-severe diarrhoea after the challenge. When analysing the complete set of analytical results, a high correlation was found among the three serum biomarkers. The most representative morphological indicator was the villus:crypt ratio (V:C), which showed a strong negative correlation with all three biomarkers. Regression analyses between faecal score and the previous variable showed linear relations. When the range of V:C was analysed, based on the quartile distribution of each serum variable, a marked increase in their concentration was observed with greater villus damage. Summarising, the combination of I-FABP, Pig-MAP and TNF-α may be useful for determining the intestinal injury degree and barrier integrity in recently weaned pigs.