The effects of bacterial overgrowth and hemorrhagic shock on mucosal immunity.

Impairment in systemic and mucosal immune function is noted after hemorrhagic shock (HS). Overgrowth of gut microflora is common after shock insults and may act as a reservoir for intensive care unit-acquired infections and subsequent remote organ failure. Secretory immunoglobulin A (IgA), the principle immunoglobulin in intestinal secretions, is the first line of defense of mucosal surfaces. Although HS and gut bacterial overgrowth are often temporarily related, their combined effect on IgA is unknown and served as the basis for this study. After sham or HS, self-filling blind loops (SFBL) were created to affect bacterial overgrowth. Intestinal secretions were obtained 7 days later from SFBL and jejunal segments for quantitative culture. Gut washings were also obtained and secretory IgA levels determined by enzyme-linked immunosorbent assay. Bacterial overgrowth in the SFBL was associated with significant increases in IgA levels in the sham group only. IgA levels were depressed in both jejunal and SFBL segments in the HS group. Impaired humoral mucosal defense may be important mechanistically in the development of nosocomial infections and organ failure after HS, particularly with concurrent gut bacterial overgrowth.