Letter: treatment for small intestinal bacterial overgrowth – where are we now?

We read with great interest the study by Shah et al.1 who performed a meta-analysis on antibiotic therapy for small intestinal bacterial overgrowth (SIBO). The effort the authors made to find data should be acknowledged. Recently, studies on the pathophysiology of intestinal microbiota have grown exponentially. However, focusing on therapy, of 1356 articles initially found, only 10 fitted the authors' criteria due to marked differences existing among them in terms of study design. To limit treatment heterogeneity, the authors analysed separately rifaximin vs. placebo studies, highlighting that there was no statistically significant difference in terms of effectiveness between these arms. This worrisome report is clearly in conflict with the daily worldwide use of rifaximin in case of symptoms, suggestive of SIBO and it is likely due to the limited number of patients enrolled. Moreover, the low number of randomised trials available forced the authors to include in their analysis studies assessing antibiotic effectiveness in patients with concomitant SIBO and functional or organic diseases. However, these latter conditions deeply impact the eradication rate and determine false-positive results on breath testing (BT). Indeed, in our study,2 we excluded such influencing variables (motility disorders, mucosal injuries, anatomical changes, therapies) that should be carefully considered in trials evaluating drug effectiveness for SIBO eradication. Finally, we have some concerns regarding the association of lactulose- with glucose-BT. To date, important data have been published against the reliability of LBT in detecting SIBO,3-5 whose diagnostic accuracy should be reconsidered by applying new restrictive criteria for SIBO positivity or combining LBT with radiological investigations.6 In conclusion, we believe that the findings of this meta-analysis should be interpreted in relation to the above criticisms. Nevertheless, this work clearly underlines the need of further RCTs on SIBO treatment with uniform methodology and including both placebo and probiotics arms. Declaration of personal and funding interests: None.