Bacterial populations contaminating the upper gut in patients with small intestinal bacterial overgrowth syndrome

OBJECTIVE: Small intestinal bacterial overgrowth syndrome (SIBOS) is charac terized by an abnormally high bacterial population level in the upper gut, exceeding 10(5) organisms/ml (5 log colony-forming unit (CFU)/ml). To under stand its origin and select an appropriate antibiotic treatment, we have an alyzed the bacterial populations contaminating the upper gut in SIBOS patie nts. METHODS: Jejunal samples of 63 consecutive patients with diarrhea or malabs orption and conditions predisposing to SIBOS were cultured and antibiotic s ensitivities determined. RESULTS: Concentrations of total, microaerophilic, and anaerobic bacteria w ere confirmed in 55 patients with SIBOS (mean +/- SE) 7.6 +/- 0.8, 7.4 +/- 0.9, and 6.1 +/- 0.7 log CFU/ml, respectively. Mean number of bacterial gen era was 4.6 +/- 0.8. The main bacteria recovered were (mean +/- SE log CFU/ ml) Streptococcus (71%; 6.4 +/- 0.8), Escherichia coil (69%; 7.2 +/- 0.9), Staphylococcus (25%; 6.2 +/- 0.6), Micrococcus (22%; 6.0 +/- 0.7), Klebsiel la (20%; 7.1 +/- 0.8), Proteus (11%; 6.1 +/- 0.8) for microaerophilic bacte ria, and Lactobacillus (75%; 6.1 +/- 1.1), Bacteroides (29%; 6.9 +/- 1.3), Clostridium (25%; 5.5 +/- 1.0), Veillonella (25%; 5.3 +/- 0.7), Fusobacteri um (13%; 4.8 +/- 0.5), and Peptostreptococcus (13%; 6.1 I 0.7) for anaerobi c bacteria. Amoxicillin-clavulanic acid and cefoxitin were efficient on >90 % of strains. CONCLUSIONS: Contaminating flora isolated in SIBOS include commonly identif ied oropharyngeal and colonic flora, but these occur in SIBOS at different levels from those usually found in their original location. These data may hopefully serve as a starting point to further therapeutic controlled studi es. (C) 1999 by Am. Cell. of Gastroenterology.