In vitro evaluation of Lactobacillus crispatus K313 and K243: High-adhesion activity and anti-inflammatory effect on Salmonella braenderup infected intestinal epithelial cell

Currently, there is an increasing interest in the use of probiotics as an alternative strategy to antimicrobial compounds. In this study, two high adhesive strains Lactobacillus crispatus K313 adhering to HT-29 cells as well as Lb. crispatus K243 adhering to collagen type IV were isolated from chicken intestines. SDS-PAGE analysis revealed the presence of the potential S-proteins SlpA and SlpB in Lb. crispatus K243 and K313. SlpA and SlpB, rich in hydrophobic amino acids, were proved to be involved in adhering to collagen type IV and HT-29 cells, respectively, based on the LiCl treatment assay. After removal of S-proteins, the viability and tolerance of the two Lb. crispatus strains to simulated gastric and small intestinal juice were reduced, indicating the protective role of S-proteins against the hostile environments. Lb. crispatus K313 exhibited the stronger autoaggregation ability and inhibitive activity against Salmonella braenderup H9812 adhesion to HT-29 cells than the strain K243. To elucidate the inhibitive mechanism, cultured epithelial cells were exposed with Lb. crispatus strains, and followed by a challenge with S. braenderup H9812. The pro-inflammatory signaling factors (IL-8, CXCL1 and CCL20) from HT-29 were detected by real-time PCR technology. The results showed that both of Lb. crispatus strains down-regulated the transcription level of those pro-inflammatory genes induced by S. braenderup H9812 by 36.2–58.8%. ELISA analysis was further confirmed that Lb. crispatus K243 and K313 inhibited the IL-8 secretion triggered by S. braenderup H9812 by 32.8% and 47.0%, indicating that the two isolates could attenuate the pro-inflammatory signaling induced by S. braenderup H9812, and have the potential application in clinical practice to prevent diarrhea.