Review Article

Small Intestinal Bacterial Overgrowth

Prevalence, Clinical Features, Current and Developing Diagnostic Tests, and Treatment

E. Grace; C. Shaw; K. Whelan; H. J. N. Andreyev


Aliment Pharmacol Ther. 2013;38(7):674-688. 

In This Article

Treatment for SIBO

The primary goal of therapy in SIBO should be the treatment of any underlying disease or structural defect, although for many conditions, this cannot be achieved. Management should include correction of any nutritional deficiencies, where present. This may involve nutritional support and/or supplemental fat-soluble vitamins, vitamin B12 and minerals. The use of prokinetic agents may be considered for patients with gastroparesis or intestinal dysmotility. However, the efficacy of these agents has not yet been proven.[87–90]

Treatment for SIBO aims to modify the GI microbiota, usually with antibiotics, in a way that will result in symptomatic improvement. Due to the limitations associated with qualitative and quantitative bacteriological studies and because the contaminating bacterial populations are quite numerous, choice of antibiotic remains primarily empiric. Effective treatment generally includes one or more drugs with activity against both aerobic and anaerobic enterobacteria.

Many different antibiotic regimens have been advocated for use in SIBO, including ciprofloxacin, metronidazole, neomycin, norfloxacin and doxycycline. There exists no consensus on the most efficacious dose or duration of treatment.[8,41,89,91] In one study, 70% of patients with SIBO showed a good response to ciprofloxacin, while a regimen of amoxicillin–clavulanic acid and cefoxitin eradicated more than 90% of strains isolated from SIBO patients.[41,92]

There has been a growing interest in the use of rifaximin (a non-absorbed rifamycin analogue) in SIBO management, especially in patients with IBS.[40,93–97] A systematic review demonstrated the efficacy and short-term safety of rifaximin for IBS patients.[98] Although, the exact mechanisms by which rifaximin improves IBS symptoms remain incompletely defined, rifaximin's benefits in IBS patients are likely, at least in part, due to alteration of the quantity, location and/or quality of the host's GI microbiota.

A systematic review of the use of rifaximin in patients testing positive for SIBO has not yet been published. Although the published data on its use in this setting does point towards the benefit of the drug in the global improvement of symptoms associated with SIBO,[99,100] further evidence in favour of rifaximin needs to be elucidated.

Given the high prevalence of primary and acquired bacterial resistance, cost of treatment, likely placebo effect and potential side effects of treatment, decisions on antibiotic management should be tailored to the individual as much as possible.

Probiotics are another potential treatment for SIBO; however, there are only pilot studies addressing their use. One open-labelled pilot study assessed the effect of Lactobacillus casei Shirota on SIBO patients, where SIBO was demonstrated by an early rise in breath H2 after lactulose.[101] Following the 6-week intervention (65 billion bacteria/day), 64% of patients no longer had a positive breath test, but there was no significant improvement in abdominal symptoms.

In another pilot study, patients were randomised to receive either a probiotic or metronidazole as treatment for SIBO.[102] The probiotic contained Lactobacillus casei,Lactobacillus plantarum,Streptococcus faecalis and Bifidobacterium brevis. A statistically significant difference in symptomatic response favoured the use of the probiotic over the antibiotic (P = 0.036). Probiotics may have a beneficial effect in this setting, but double-blind, randomised, placebo-controlled trials are essential to demonstrate their dose effects and clinical relevance.