[Bifidobacterial supplement enhances the expression and excretion of intestinal sIgA in severely burned rats]

To investigate the potential effect of bifidobacterial supplement on intestinal mucosal immunity associated with severe burns.

Wistar rats were randomly divided into burn control group (BC group, n = 30), treatment group (BT group, n = 30), and sham-burn group (NC group, n = 10). Rats in BT group were fed bifidobacterial preparation (5 x 10(9) CFU/ml) after 30% total body surface area full-thickness burns, 1.5 ml, twice daily. Rats in BC group and NC group were fed normal saline, 1.5 ml, twice daily. Samples were taken on post-burn 1-, 3-, and 5-day. The incidence of bacterial translocation and bifidobacteria counts in the cecum mucosa were determined with standard methods. The sIgA levels in the mucus of the small intestine were measured by RIA. The positive sIgA expression in the lamina propria was detected by immunohistochemical staining.

The incidence of bacterial translocation was 42% and 16% in BC and BT groups on post-burn day 3 (P = 0.004), 30% and 8% on day 5 (P = 0.002), respectively. Plasma endotoxin levels were markedly higher in BC and BT groups than in NC group at the early stage post-burn. There was a significant decrease between BT group and BC group on post-burn day 1 (P = 0.0412). Bifidobacteria counts in cecum mucosa were reduced by 10- to 60-fold after thermal injury, but there was a remarkable increase in bifidobacteria counts in animals fed with bifidobacteria. sIgA levels in the intestinal mucus were significantly decreased in group BC, but they returned to normal range in BT group on post-burn day 5. Similarly, sIgA expression in the lamina propria was also weakened after burns, and had a tendency to recover after prescription of a 5-day bifidobacteria-supplemented formula. A strong positive correlation was observed between the counts of bifidobacteria in the cecal mucosa and the levels of sIgA in the intestinal mucus (r = 0.7534, P = 0.0000).

The expression and excretion of sIgA in the intestine appear to be markedly inhibited following a severe thermal injury. The supplement of exogenous bifidobacteria could improve sIgA formation in the small intestine, thereby reducing the incidence of bacterial/endotoxin translocation secondary to major burns.