Interaction with enteric pathogens and toxins

The first major line of defence that the body has against enteric pathogens is the mucosal surface lining of the gastrointestinal tract - it is at this layer that pathogenic bacteria succeed in binding to the gut surface. 

reuteri is a member of the consortium of bacteria involved in kefir production (Heller, 2001). Amongst 58 strains of Lactobacillus species isolated from kefir, approximately 19% of the isolates showed the ability to bind to Caco-2 cells by competitive binding with Salmonella typhimurium (Santos, San Mauro, Sanchez, Torres, Marquina, 2003). This area still remains unexplored for determining whether EPS, known to be secreted by some of these strains, is indeed the causative agent Lactobacillus plantarum is not often associated with fermented dairy products, but it has been isolated as one of the major species from a traditional milk of the Maasai (Mathara et al., 2008) Lb. plantarum (strain LP6) was determined to bind to rat intestinal mucus 

EPSs have been reported to elicit an immune response against viruses, as well. The acidic fraction of EPS isolated from L. delbrueckii subsp. bulgaricus (OLL1073R-1) was shown to demonstrate antiviral activity against the influenza vims A/PR/8/34 (HlNl) in BALB/c mice via its immunopotentiating activity (Nagai, Makino, Ikegami, Itoh, Yamada, 2011). 

EPS produced from some fermented milk products, although in relatively small quantities, influences the rheology of their matrix, and has also been hypothesised to provide a barrier that slows down the movement of phages (Moineau et al.,1996) and antimicrobial compounds. 

It seems, then, that through a variety of mechanisms, some EPSs from LAB have the abihty to retard or diminish the effects of gut pathogens, either through a direct interaction with them, acting as decoys, or by binding to the epithelial surface of the gut. 

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