Enteric bacterial flora and bacterial overgrowth syndrome.

Under certain conditions, colonic bacterial flora can colonize the upper small bowel in concentrations sufficient to cause mucosal damage and malabsorption of nutrients, vitamin B12, and fat-soluble vitamins. This situation, known as small bowel bacterial overgrowth syndrome (SBBOS) may be an under-appreciated cause of malnutrition in elderly people. The diagnosis of SBBOS should be considered when patients with known or suspected predisposing conditions have symptoms or findings compatible with this syndrome. However, proof of small bowel bacterial overgrowth requires specialized testing that is not readily available. Moreover, disagreement persists as to how best to test definitively for this disease. Therefore, on a practical level and despite the potential drawbacks of such a decision, SBBOS is usually diagnosed when a compatible syndrome responds to an empirical trial of appropriate oral antibiotics. Improvements on this approach to SBBOS will be built on more widespread access to sensitive, specific, and less cumbersome testing than is currently available.