Screening the ability of natural feed ingredients to interfere with the adherence of enterotoxigenicEscherichia coli(ETEC) K88 to the porcine intestinal mucus

Abstract

The inhibition of the attachment of bacteria to the intestine by receptor analogues could be a novel approach to prevent enterotoxigenic Escherichia coli (ETEC) K88-induced diarrhoea in piglets. The objective of the present study was to screen the ability of different feed ingredients (FI) to bind to ETEC K88 (adhesion test, AT) and to block its attachment to the porcine intestinal mucus (blocking test, BT) using in vitro microtitration-based models. In the AT, wheat bran (WB), casein glycomacropeptide (CGMP) and exopolysaccharides exhibited the highest adhesion to ETEC K88 (P,0·001). In the BT, WB, CGMP and locust bean (LB) reduced the number of ETEC K88 attached to the intestinal mucus (P,0·001). For WB and LB, fractionation based on their carbohydrate components was subsequently carried out, and each fraction was evaluated individually. None of the WB fractions reduced the adhesion of ETEC K88 to the mucus as did the original extract, suggesting that a protein or glycoprotein could be involved in the recognition process. With regard to the LB fractions, the water-extractable material reduced the adhesion of ETEC K88 (P, 0·001) to the mucus similar to the original extract (P, 0·001), indicating, in this case, that galactomannans or phenolic compounds could be responsible for the recognition process. In conclusion, among the FI screened, the soluble extracts obtained from WB, LB and CGMP exhibited the highest anti-adhesive properties against ETEC K88 in the BT. These results suggest that they may be good candidates to be included in diets of weaned piglets for the prevention of ETEC K88-induced diarrhoea.Key words: Enterotoxigenic Escherichia coli K88: Natural feed ingredients: Antiadhesives: Porcine intestinal mucus: Piglets Colibacillosis caused by the strains of enterotoxigenic Escherichia coli (ETEC) is a common diarrhoeic disease in neonatal and early weaned pigs (1) and is the most important disease worldwide in the swine industry (2) . Specifically, ETEC K88 serotype, which expresses fimbrial adhesin F4, is the most prevalent serotype responsible for this disease. The susceptibility of piglets to ETEC K88 is inherited as an autosomal dominant trait and is determined by the expression of receptors on the enterocyte brush borders (3) . So, the recognition of the intestinal receptors by the bacterial fimbriae and the attachment of E. coli to the brush border of epithelial cells are considered as the primary requisites for the pathogenesis of colibacillosis. After attachment, ETEC K88 can also produce enterotoxins that induce water and electrolyte secretion into the intestinal lumen, resulting in dehydration and metabolic acidosis (4) .Receptors for ETEC K88 fimbriae appear to be glycoconjugates, which are sparsely located on the mucosal surface of the small intestine of piglets, preferentially in the ileum (5) . Different antigenic variants, referred to as K88ab, K88ac and K88ad fimbriae, bind to their own set of receptors. Whereas the K88ab and K88ac adhesins preferentially bind to glycoproteins, t...

Exopolysaccharides Synthesized by Lactobacillus reuteri Protect against Enterotoxigenic Escherichia coli in Piglets

“…Some dietary carbohydrates prevent pathogen adhesion, possibly by acting as receptor analogs that saturate the glycan-binding domains of bacterial lectins and thus prevent binding to host glycoproteins. For example, polysaccharides extracted from green olive fermentation brines prevented adhesion of ETEC K88 to IPEC-J2 cells (18) but not to intestinal mucus (35). Glycans evaluated in vivo by using the SISP model were often classified only as ethanol-soluble and ethanol-insoluble fractions derived from hydrolysis of soybean and canola meal (31) or crops (27).…”

Recent advances in adherence and invasion of pathogenic Escherichia coli

“…Recently, Zhou et al have demonstrated that deletion of fliC (encoding the major flagellin protein) and/or the faeG (encoding the F4 major fimbrial subunit) from ETEC strain C83902 significantly reduced its ability to adhere to porcine epithelia IPEC-J2 cells, but also impacting biofilm formation and quorum sensing (32). Interestingly, another study found an alternative way to block the adherence of ETEC K88 to IPEC-J2 by using ETEC anti-adhesives, including casein glycomacropeptide, exopolysaccharide, and vegetable extract (locust bean or wheat bran) (33). Finally, studies with human milk and commercial infant formulas found that the main gangliosides (GM3, GD3, GM1) and free sialic acid (Neu5Ac) are able to impede the adhesion of several pathogenic bacteria, including ETEC (26).…”

Effects of medium-chain fatty acids on the structure and immune response of IPEC-J2 cells

“…High efforts are carried out in the search of alternatives to substitute or decrease the use of antibiotics in animal production (Allen et al 2013;Seal et al 2013). In pig production, a diverse range of feed additives has been tested like probiotics, zinc, organic acids, plant extracts, microbial by-products or dairy products and others (Roselli et al 2005;González-Ortiz et al 2014;Pluske 2013;Spitzer et al 2014). …”