BackgroundA possible role of gut bacteria and their metabolic by-products in the development of coronary artery disease (CAD) is suspected. There is a lack of studies evaluating the association of small intestinal bacterial overgrowth (SIBO) with the development of CAD.AimTo evaluate the frequency and risk factors for angiography-confirmed CAD in patients with or without SIBO.MethodsA total of 1059 patients tested for SIBO using the glucose hydrogen/methane breath test from 2006 to 2014 were evaluated. In total, 160 had coronary artery angiography and were included in the study. SIBO-positive patients were compared to SIBO-negative patients. Demographic, clinical, and laboratory variables and the presence of CAD on coronary angiography were analyzed.ResultsPatients with SIBO had a higher frequency of CAD (78.9 vs. 38.6%, p < 0.001), diabetes mellitus (40.0 vs. 22.9%, p = 0.016), chronic kidney disease (26.7 vs. 12.9%, p = 0.025), use of angiotensin conversion enzyme inhibitor/blocker (45.5 vs. 32.9%, p = 0.008), and statins (75.6 vs. 61.4%, p = 0.004). Patients with SIBO had an increased number of coronary arteries affected compared to SIBO-negative patients (1-vessel disease 67.2 vs. 32.8%, p < 0.001; 2-vessel disease 85.7 vs. 14.3%, p < 0.001; and 3-vessel disease 82.4 vs. 17.6%, p < 0.001, respectively). In the stepwise multivariate logistic regression analysis, SIBO remained an independent risk factor for CAD (odds ratio 7.18, 95% confidence interval 3.09–16.67; p < 0.001).ConclusionSIBO was found to be associated with CAD and with the number of coronary arteries involved in this study from a single tertiary center. Further studies are necessary to confirm the association of SIBO with CAD. In the presence of risk factors, patients with SIBO may benefit from assessment for CAD.