Small intestinal mucosal immunity and morphometry in luminal overgrowth ofindigenous gut flora

OBJECTIVE: The aim of this study was to investigate the separate effects of indigenous oropharyngeal- and colonic-type flora on small intestinal mucos al immunity and morphometry in small intestinal bacterial overgrowth (SIBO) . METHODS: A duodenal aspirate and random biopsies of underlying mucosa were obtained from 52 adult subjects (age range, 18-90 yr; median, 60 yr) withou t disorders that may otherwise disturb small intestinal histology or mucosa l immunity. Villus height, crypt depth, villus/crypt ratios, counts of intr aepithelial lymphocytes (IELs) and lamina propria total mononuclear cells, IgA, IgM, and IgCr plasma cells, mast cells, and B and T lymphocytes were d etermined in relation to the presence or absence of SIBO and the nature of the overgrowth flora in all subjects. CD4+ve and CD8+ve T-cell counts were determined in 24 subjects. RESULTS: SIBO was present in 26 of 52 (50%) subjects. Overgrowth flora incl uded colonic-type bacteria in 20 subjects and oropharyngeal-type flora alon e in 6 subjects. Lamina propria IgA plasma cell counts were significantly i ncreased in subjects with SIBO, irrespective of whether the overgrowth flor a comprised oropharyngeal-type flora alone or included colonic-type bacteri a. Neither villus height, crypt depth, villus/crypt ratios, nor total or ot her mononuclear cell counts in lamina propria differed significantly betwee n subjects with and without SIBO, irrespective of the nature of the overgro wth flora. IEL counts were significantly higher than in culture-negative su bjects only when the overgrowth flora included colonic-type bacteria. Even then, IEL counts were within a range currently considered normal. A signifi cant, inverse correlation between advancing age and IEL counts became appar ent after adjusting for the effect of SIBO of colonic-type flora. CONCLUSIONS: SIBO of oropharyngeal- and colonic-type flora are associated w ith differing disturbances of local duodenal mucosa. Nonetheless, these wou ld not be readily apparent during routine histological assessment. Old age independently influences duodenal IEL counts. (C) 2001 by Am. Cell. of Gast roenterology.