SMALL-INTESTINAL BACTERIAL OVERGROWTH IN THE SYMPTOMATIC ELDERLY

Objectives: 1) To determine the prevalence of small intestinal overgro wth with colonic-type bacteria in symptomatic elderly subjects, partic ularly those without important ''clues'' such as clinically apparent p redisposition or vitamin B-12 deficiency, and 2) to investigate defens e mechanisms such as gastric acidity, small intestinal motility, and l uminal IgA in this setting. Methods: Fifty-two symptomatic subjects, w ithout vitamin B-12 deficiency or clinically apparent predisposition t o bacterial overgrowth or disturbed mucosal immunity, including 22 sub jects greater than or equal to 75 yr old, underwent culture of small i ntestinal luminal secretions. Indicator paper was used to measure fast ing gastric pH. The presence of bacteria of confirmed nonsalivary orig in in small intestinal secretions served as an index of small intestin al dysmotility. Small intestinal luminal IgA concentrations were measu red by radial immunodiffusion. Results: Small intestinal overgrowth wi th colonic-type flora was not present in any subject investigated for dyspepsia, irrespective of age. In subjects with chronic diarrhea, ano rexia, or nausea, overgrowth with colonic-type nora (Enterobacteriacea e) was present in 0/12 (0%), 1/10 (10.0%), and 9/14 (64.3%) subjects a ged < 50 yr, 50-74 yr, and greater than or equal to 75 yr, respectivel y. Enterobacteriaceae were not concurrently recovered from saliva of a ny subject greater than or equal to 75 yr old with small intestinal ov ergrowth with these bacteria. Fasting hypochlorhydria was present in o nly 1/9 (11.1%) such subjects. Luminal IgA concentrations were signifi cantly greater in subjects greater than or equal to 75 yr old with bac terial overgrowth than in culture-negative subjects (p less than or eq ual to 0.003). Conclusions: Small intestinal overgrowth with colonic-t ype bacteria should be considered in subjects greater than or equal to 75 yr old with chronic diarrhea, anorexia, or nausea, even in the abs ence of clues such as clinically apparent predisposition or vitamin B- 12 deficiency. Small intestinal dysmotility, rather than fasting hypoc hlorhydria or mucosal immunosenescence, probably is responsible for th e prevalence of bacterial overgrowth in this group.