Effects of a partially digested whey protein concentrate on Salmonella enterica serotype Typhimurium adhesion to Caco-2 cells

Can proteins, protein hydrolysates and peptides cooperate with probiotics to inhibit pathogens?

Studies have shown that probiotics can effectively inhibit pathogens in the presence of proteins, protein hydrolysates and peptides (protein derivates). However, it is still unclear the modes of probiotics to inhibit pathogens regulated by protein derivates. Therefore, we summarized the possible effects of protein derivates from different sources on probiotics and pathogens. There is abundant evidence that proteins and peptides from different sources can significantly promote the proliferation of probiotics and increase their secretion of antibacterial substances. Such proteins and peptides can also stimulate the adhesion of probiotics to intestinal epithelial cells and contribute to regulating intestinal immunity, but they seem to have the negative effects on pathogens. Moreover, a direct effect of proteins on intestinal cells is summarized. Whether or not they can cooperate with probiotics to inhibit pathogens using above possible mechanisms were discussed. Furthermore, there seems to be no consistent conclusions that protein derivates have synergistic effects with probiotics, and there is still limited evidence on the inhibiting patterns. Therefore, the existing problems and shortcomings are noted, and future research direction is proposed.

Influence of sweet whey protein concentrate and its hydrolysates on host-pathogen interactions in the emerging foodborne pathogen Cronobacter sakazakii

AIMS

Antimicrobial resistance poses a significant global healthcare predicament. An attractive approach to the dilemma of drug-resistant bacteria is the development and use of agents that interfere with the ability of pathogens to adhere to human tissue. The influence of sweet whey protein concentrate (SWPC), and selected hydrolysates of this material, on host-pathogen interactions of Cronobacter sakazakii (ATCC 29544) was investigated.

METHODS AND RESULTS

CaCo-2 cell line was selected as a suitable model for the human intestinal epithelium. Cronobacter sakazakiiATCC 29544 was identified as the strain with the highest adhesion efficiency. SWPC reduced its association by 80% (P < 0·01), invasion 35% (P < 0·01), and translocation >95% (P < 0·001). SWPC enzymatically modified with lipase, trypsin and pepsin had variable effects on these behaviours with the most significant effect exhibited with the lipase treatment. SWPC produced an almost total inhibition of translocation of C. sakazakii across a CaCo-2 cell monolayer. Lipase and pepsin treated SWPC also reduced translocation by 75% and 90% respectively. However, trypsin treatment nullified the effect SWPC had on translocation. The presence of viable bacterial cells and SWPC both increased expression of IL-8 following Cronobacter invasion into CaCo-2 cells.

CONCLUSIONS

Factors governing adherence, invasion and translocation of Cronobacter spp. to human intestinal cells are multi-factorial and digested milk products exhibit varying effects dependant on their enzyme modification and protein lipid content.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings contribute to our, as yet, incomplete understanding of Cronobacter pathogenesis, and suggest that SWPC in whole and enzymatically hydrolysed forms, may provide a cost-effective source of bioactive materials with inhibitory effects on bacterial virulence.

Dietary supplementation with soluble plantain non-starch polysaccharides inhibits intestinal invasion of Salmonella Typhimurium in the chicken

Soluble fibres (non-starch polysaccharides, NSP) from edible plants but particularly plantain banana (Musa spp.), have been shown in vitro and ex vivo to prevent various enteric pathogens from adhering to, or translocating across, the human intestinal epithelium, a property that we have termed contrabiotic. Here we report that dietary plantain fibre prevents invasion of the chicken intestinal mucosa by Salmonella. In vivo experiments were performed with chicks fed from hatch on a pellet diet containing soluble plantain NSP (0 to 200 mg/d) and orally infected with S.Typhimurium 4/74 at 8 d of age. Birds were sacrificed 3, 6 and 10 d post-infection. Bacteria were enumerated from liver, spleen and caecal contents. In vitro studies were performed using chicken caecal crypts and porcine intestinal epithelial cells infected with Salmonella enterica serovars following pre-treatment separately with soluble plantain NSP and acidic or neutral polysaccharide fractions of plantain NSP, each compared with saline vehicle. Bacterial adherence and invasion were assessed by gentamicin protection assay. In vivo dietary supplementation with plantain NSP 50 mg/d reduced invasion by S.Typhimurium, as reflected by viable bacterial counts from splenic tissue, by 98.9% (95% CI, 98.1-99.7; P<0.0001). In vitro studies confirmed that plantain NSP (5-10 mg/ml) inhibited adhesion of S.Typhimurium 4/74 to a porcine epithelial cell-line (73% mean inhibition (95% CI, 64-81); P<0.001) and to primary chick caecal crypts (82% mean inhibition (95% CI, 75-90); P<0.001). Adherence inhibition was shown to be mediated via an effect on the epithelial cells and Ussing chamber experiments with ex-vivo human ileal mucosa showed that this effect was associated with increased short circuit current but no change in electrical resistance. The inhibitory activity of plantain NSP lay mainly within the acidic/pectic (homogalacturonan-rich) component. Supplementation of chick feed with plantain NSP was well tolerated and shows promise as a simple approach for reducing invasive salmonellosis.