Introduction Choice of antibiotic treatment in patients who test positively for Small Intestinal Bacterial Overgrowth (SIBO) can be difficult. No controlled trial has examined the clinical efficacy of antibiotics in SIBO. This study aimed to identify which antibiotics are the most effective in treating SIBO in a real world retrospective cohort.

Methods 520 adult patients (360 female, 160 male, mean age 49) who underwent hydrogen and glycocholate-methane breath tests for a suspicion of SIBO between the dates 01/01/2010 and 31/12/2013 were evaluated. The clinical information of patients who tested positively in both tests was recorded. Information was also gathered as to the antibiotic they were prescribed and whether they received symptomatic benefit from their treatment.

Results A total of 90 patients who tested positive were prescribed antibiotics (59 female, 31 male, mean age 56). 69 (76.7%) of these patients benefitted from their management. 32 patients who tested positive were given cyclical antibiotics. The efficacy of cyclical antibiotics compared with the combined efficacy rates of other antibiotic regimes in treating patients with a positive breath test result was 93.8%. (93.8% vs 67.2%, Chi-square = 8.1, p = 0.004). 15 patients who tested positive were given rifaximin. The efficacy of rifaximin in treating patients with a positive breath test result compared with the combined efficacy of other antibiotic regimes was 80%. (80% vs 76% Chi-square = 0.112, p = 0.738). 18 patients who tested positive were given metronidazole. The efficacy of metronidazole in treating patients who tested positive in the breath tests compared with combined efficacy rates of other antibiotics was much lower at 50% (50% vs 83%, Chi-square = 8.9441, p = 0.0028).

Conclusion Metronidazole appeared inferior to rifaximin monotherapy for treating SIBO. Cyclical antibiotics appeared most effective. These findings should be explored further in randomised controlled prospective trials to determine the optimal treatment regime.

Disclosure of Interest None Declared