To investigate the effect and related mechanism of faecal microbiota transplantation (FMT) on intestinal barrier function in severely burned rats.

Thirty-six male SD rats aged 6-8 weeks were divided into 3 groups according to the random number table method, normal group (n=12), pure burn group (n=12) and FMT intervention group (n=12). Thirty percent total body surface area full thickness burn model was made for rats in pure burn group and FMT intervation group, rats in normal group were not injured. Rats in pure burn group and FMT intervention group were resuscitated by intraperitoneal injection of balanced salt solution 40 mL/kg immediately after burn. Fresh faecal samples of the normal group rats were collected 10 g and made into faecal filtrate. At 1 h after injury, rats in the FMT intervention group was given faecal filtrate by gavage(10 mL/kg), and the same dose of faecal filtrate was given again 12 h later. Rats in normal group and pure burn group were given the same amount of 0.9% sodium chloride solution at the same time. At 24 and 72 h after injury, 1 mL fresh faecal samples from the colon of rats in each group were collected, and the level of intestinal flora was detected by real-time fluorescence quantification-polymerase chain reaction, namely, the number of Bifidobacteria, Bacteroides fragilis, Lactobacillus, Escherichia coli and Enterococcus. The prepared plasma of rats was taken, and luciferin isothiocyanate (FITC) -glucan permeability test was used to detect the intestinal permeability of rats in each group. The levels of diamine oxidase, D-lactic acid, interleukin (IL)-6, tumor necrosis factor (TNF)-α and IL-10 in serum were detected by enzyme-linked immunosorbent assay (ELISA). At 24 and 72 h after injury, about 1 cm of the terminal ileum tissue of rats in each group were taken respectively, and the morphological structure of intestinal mucosa was observed by hematoxylin-eosin staining. Data were processed by one-way ANOVA and t test.

(1)The differences in the number of Bifidobacteria, Bacteroides fragilis, Lactobacillus, Escherichia coli and Enterococcus in the three groups at 24 and 72 h after injury were statistically significant (P<0.05). At 24 h after injury, the numbers of Bifidobacteria, Bacteroides fragilis, Lactobacillus, Escherichia coli and Enterococcus in the pure group were (2.76±0.15), (3.27±0.40), (2.33±0.33), (7.06±0.49), (6.42±0.50) LogN/g, respectively, and those in the FMT intervention group were (3.18±0.16), (4.52±0.58), (2.92±0.28), (6.14±0.47), (5.28±0.43) LogN/g, respectively; at 72 h after injury, the numbers of Bifidobacteria, Bacteroides fragilis, Lactobacillus, Escherichia coli and Enterococcus in the pure burn group were (3.16±0.19), (3.79±0.42), (2.64±0.43), (6.34±0.56), (5.56±0.61) LogN/g, respectively, and those in the FMT intervention group were(3.53±0.25), (5.50±0.32), (3.26±0.39), (5.37±0.70), (4.10±0.85) LogN/g, the numbers of Bifidobacteria, Bacteroides fragilis and Lactobacillus in FMT intervention group were higher than those in pure burn group, and the numbers of Escherichia coli and Enterococcus in FMT intervention group were lower than those in pure burn group, the differences were statistically significant (P<0.05). (2) At 24 h after injury, the intestinal permeability of rats in normal group, pure burn group and FMT intervention group were 0.94±0.16, 2.39±0.37 and 1.58±0.33, respectively; at 72 h after injury, the intestinal permeability of rats in normal group, pure burn group and FMT intervention group were 0.94±0.17, 1.88±0.57 and 1.21±0.24, respectively, the differences among the three groups at the two phase points were statistically significant (F=34.092, 7.064; P<0.05). Compared with the pure burn group, the intestinal permeability in FMT intervention group was decreased at 24 and 72 h after injury, and the differences were statistically significant (t= 3.971, 2.664; P <0.05). (3) At 24 and 72 h after injury, the differences of the levels of diamine oxidase, D-lactic acid and IL-6, TNF-α and IL-10 in serum of the 3 groups were statistically significantly (P<0.05). At 24 h after injury, the levels of diamine oxidase and D-lactic acid in serum of FMT intervention group were (0.93±0.13) U/mL and (3.54±0.78) μmol/L, respectively, and at 72 h after injury were (0.55±1.15) U/mL and (2.58±0.51) μmol/L, respectively, which were lower than those in the pure burn group at 24 h after injury [(1.28±0.18) U/mL, (4.83±0.57) μmol/L] and at 72 h after injury [(0.86±0.21) U/mL, (4.13±0.55) μmol/L], the differences were statistically significant (P<0.05). At 24 and 72 h after injury, compared with the pure burn group, the levels of IL-6 and TNF-α in the serum of rats in the FMT intervention group decreased, and the levels of IL-10 increased, the differences were statistically significant (P<0.05). (4)At 24 and 72 h after injury, the intestinal mucosal epithelium of normal group rats was intact without inflammatory cell infiltration; at 24 h after injury, intestinal mucosal villi in the FMT intervention group was slightly shorter and disordered, scattered epithelial cells was destroyed and mucous membranes was shed, there was infiltration of inflammatory cells, compared with the pure burn group, intestinal mucosal damage was reduced. At 72 h after injury, the intestinal mucosa epithelium of the FMT intervention group was basically intact, with a small amount of inflammatory cells infiltration, and the intestinal mucosa repair was more obvious than that of the pure burn group.

The disturbance of intestinal flora, exacerbation of systemic inflammatory response and the impairment of intestinal mucosal barrier function can occur in severely burned rats at early stage, FML can improve intestinal flora disturbances, restrain inflammatory response, and protect the intestinal barrier function.