Risk Factors Associated With Upper Aerodigestive Tract or Coliform Bacterial Overgrowth of the Small Intestine in Symptomatic Patients

Introduction: The clinical relevance of bacterial types identified in small bowel aspirate cultures during diagnostic evaluation of small intestinal bacterial overgrowth (SIBO) is unclear.

Aim: The main purpose of this study was to assess associations between risk factors for upper aerodigestive tract (UAT) or coliform SIBO and SIBO diagnosis by culture.

Materials And Methods: Small bowel aspirates were cultured in patients with suspected SIBO, defined as ≥10 colony-forming units/mL coliform or ≥10 colony-forming units/mL UAT bacteria. History was reviewed for risk factors and potential SIBO complications. Symptoms, quality of life, psychological traits, and laboratory values were assessed. We compared groups by 2-sample t test, Wilcoxon rank sum test, and the Fisher exact test. Overall associations of primary and secondary endpoints with type of bacterial overgrowth were assessed by analysis of variance F-test, Kruskal-Wallis test, and the Fisher exact tests. Associations of risk factors with type of overgrowth were explored using multinomial logistic regression.

Results: Among 76 patients, 37 had SIBO (68% coliform, 33% UAT) and 39 did not. Conditions (P=0.02) and surgery (P<0.01) associated with decreased gastric acid were associated with SIBO. In multinomial logistic regression, conditions of decreased acid was associated with UAT SIBO [odds ratio (OR), 5.8; 95% confidence interval, 1.4-33.3]. Surgery causing decreased acid was associated with UAT [OR, 9.5 (1.4-106)] and coliform SIBO [OR, 8.4 (1.6-86.4)]. Three patients with discontinuous small bowel had coliform SIBO [OR, 17.4 (1.2-2515)]. There were no differences in complications, overall symptoms, quality of life, or psychological traits.

Conclusions: Conditions or surgeries associated with decreased gastric acid are associated with SIBO diagnosis by culture.