The intestine is a particularly dynamic environment in which the host constantly interacts with trillions of symbiotic bacteria called the microbiota. Using quorum sensing (QS) communication, bacteria can coordinate their social behavior and influence host cell activities in a non-invasive manner. Nowadays, a large amount of research has greatly spurred the understanding of how bacterial QS communication regulates bacterial cooperative behaviors due to coexistence and host-microbe interactions. In this review, we discuss bacterial QS in the gut and its role in biofilm formation. As a biological barrier, the mucosal immune system can effectively prevent pathogenic microorganisms and other immunogenic components from entering the internal environment of the host. We focus on the relationship between biofilm and intestinal mucosal immunity, and how probiotic bacteria may regulate them. This review is to provide a theoretical basis for the development of new techniques including probiotics targeting the intestinal barrier function, thereby improving gut health.

The ability to adhere to the intestinal mucus layer is an important property of probiotic bacteria. Lactobacillus reuteri strains ZJ615 and ZJ617 show low and high adhesion, respectively, to intestinal epithelial cells. In this study, we quantified bacterial cell wall-associated glyceraldehyde-3-phosphate dehydrogenases (cw-GAPDH) and bacterial cell membrane permeability in both strains using immunoblotting and flow cytometry, respectively. Highly adhesive L. reuteri ZJ617 possessed significantly more cw-GAPDH, higher cell membrane permeability, and significantly higher adhesive ability toward mucin compared with low-adhesive L. reuteri ZJ615. In vitro adhesion studies and analysis of interaction kinetics using the Octet, the system revealed significantly decreased interaction between L. reuteri and mucin when mucin was oxidized when bacterial surface proteins were removed when bacteria were heat-inactivated at 80 °C for 30 min, and when the interaction was blocked with an anti-GAPDH antibody. SWISS-MODEL analysis suggested intensive interactions between mucin glycans (GalNAcα1-O-Ser, GalNAcαSer, and Galβ3GalNAc) and GAPDH. Furthermore, in vivo studies revealed significantly higher numbers of bacteria adhering to the jejunum, ileum, and colon of piglets orally inoculated with L. reuteri ZJ617 compared with those inoculated with L. reuteri ZJ615; this led to a significantly decreased rate of diarrhea in piglets inoculated with L. reuteri ZJ617. In conclusion, there are strong correlations among the abundance of cw-GAPDH in L. reuteri, the ability of the bacterium to adhere to the host, and the health benefits of this probiotic.

The aim of this study was to determine the effects of dietary inclusion of the combination of tributyrin with oregano or methyl salicylate as a substitute to antibiotics on gut health and microbiota of piglets. A total of 48 weaned crossbred piglets (Duroc × Large White × Landrace, 8.79 ± 0.97 kg, 21 ± 1 d) were randomly allocated to four experimental groups and fed for 4 weeks: the basal diet (Con); the control plus antibiotics (AB); the control plus oregano and tributyrin (OT); and the control plus methyl salicylate and tributyrin (MT). Although a numerical improvement on feed intake, weight gain and feed conversion ratio was observed in the OT and MT as well as the AB group, the difference was not significant (p > 0.05). The OT and MT groups were larger in villus height in the duodenum compared to the Con (p < 0.05), and were larger in relative abundance of Firmicutes/Bacaeroides in the intestine compared to Con and AB groups (p < 0.01). The amount of major different metabolites was 6, 8 and 8 for the AB, OT and MT groups when compared to the Con, respectively. In conclusion, as a substitute for antibiotics the inclusion of the combination of tributyrin with either oregano or methyl salicylate to the diet of weaned piglets improved the intestinal morphological structure and altered intestinal microbiota and metabolites, which were beneficial to the animal health.

Tributyrin and essential oils have been used as alternatives to antimicrobials to improve gut health and growth performance in piglets. This study was to evaluate the effects of a dietary supplement with two encapsulated products containing different combinations of tributyrin with oregano or with methyl salicylate on growth performance, serum biochemical parameters related to the physiological status, intestinal microbiota and metabolites of piglets. A total of 108 weaned crossbred piglets (Yorkshire × Landrace, 21 ± 1 d, 8.21 ± 0.04 kg) were randomly divided into three groups. Piglets were fed with one of the following diets for 5 weeks: a basal diet as the control (CON); the control diet supplemented with an encapsulated mixture containing 30% of methyl salicylate and tributyrin at a dosage of 3 kg/t (CMT); and the control diet supplemented with an encapsulated mixture containing 30% of oregano oil and tributyrin at a dosage of 3 kg/t (COT). At the end of the feeding trial, six piglets from each group were slaughtered to collect blood and gut samples for physiological status and gut microbiological analysis. The study found that the CMT group was larger in feed intake (FI) (p < 0.05), average daily gain (ADG) (p = 0.09), total protein (TP), albumin (ALB), glutathione peroxidase (GSH-PX) (p < 0.05), blood total antioxidant capacity (T-AOC) (p < 0.05), and crypt depth in the ileum (p < 0.05) compared with the CON group. The genus abundance of Tissierella and Campylobacter in the CMT group was significantly decreased compared with the CON group. The CMT group also resulted in significantly higher activity in amino acid metabolism and arginine biosynthesis compared with the CON group. The COT group was larger in T-AOC, and the genus abundance of Streptophyta and Chlamydia was significantly increased in the ileum compared with the CON group. Data analysis found a significantly high correlation between the genus abundance of Chlamydia and that of Campylobacter in the ileum. The genus abundance of Campylobacter was also positively correlated with the sorbitol level. In general, the results indicated that the supplementation of both encapsulated mixtures in diet of weaned piglets could improve the animal blood antioxidant capacity. Additionally, the encapsulated mixture of methyl salicylate plus tributyrin improved the growth performance and resulted in certain corresponding changes in nutrient metabolism and in the genus abundance of ileum microbial community.

Background: The olive extract contains compounds with antioxidant and anti-inflammatory properties. This study was designed to investigate whether olive cake extract, enriched with maslinic acid and hydroxytyrosol, alleviates the lipopolysaccharides (LPS)-induced oxidative stress, inflammation and intestinal villus damage in piglets.Methods: Thirty weaned piglets (6.9±0.9 kg) were assigned to five groups using a randomized complete block design. Piglets were fed a basal diet before intraperitoneal (i.p.) injection of physiological saline (C); fed a basal diet alone (CL) or fed a basal diet plus olive extract (OL), antibiotics (AL), or olive extract and antibiotics (OAL) before i.p. injection of LPS. The feeding lasted for 2 weeks. Piglets were euthanized 4h after LPS injection. Systemic anti-oxidant and inflammation levels were measured and villus morphology in the intestine was examined.Results: Compared with those in the C group, piglets in the CL group had significantly lower GSH-Px, SOD, ALB levels and higher MDA, NO, LDH, ALT and AST levels in the serum (P<0.05). Compared with the CL group, piglets in OL, AL, and OAL groups had significantly higher serum GSH-Px, SOD and ALB levels and lower MDA, NO, LDH, ALT and AST levels (P<0.05). LPS administration significantly increased the serum concentration of TNF-α, IL-6, DAO and D-xylose in the CL group compared with the control group (P<0.05). Piglets in OL, AL, and OAL groups had significantly lower serum TNF-α, IL-6, DAO and D-xylose levels and higher IL-10 level (P<0.05). In the duodenum and ileum of piglets, LPS challenge led to significantly lower villus height (VH), higher crypt depth (CD) and lower VH/CD compared with the control group (P<0.05), whereas, OL, AL, and OAL groups had significantly lower CD and higher VH/CD compared with the CL group (P<0.05). Dietary inclusion of olive extract increased the relative abundance of intestinal Lactobacillus and Clostridium at genus level.Conclusion: Dietary supplementation with olive extract maslinic acid and hydroxytyrosol improved anti-oxidative and anti-inflammatory capacity, intestinal structure morphology, and increased the abundance of beneficial intestinal bacteria in weaned piglets challenged by LPS.