Background a nd A ims: The prevalence of small intestinal
bowel bacterial o vergrowth (SIBO) i n patients w ith irritable
bowel syndrome (IBS) ranges from 43% to 78% as determined
by t he lactulose hydrogen breath (LHBT) t est. Although
rifaximine, a non-absorbable antibiotic, h as b een able to
decrease I BS s ymptoms i n placebo-controlled r andomized
trials, these results were not repeated in phase IV studies. We
aimed to assess the prevalence of SIBO in an IBS cohort and
to evaluate the response to rifaximin.
Methods: I BS p atients f ulfilled Rome III criteria, had an
absence of alarm symptoms, n ormal f ecal c alproectin, and
normal e ndoscopic workup. They underwent lactulose
hydrogen breath t esting (LHBT) for SIBO diagnosis. P atients
with SIBO were t reated w ith rifaximine tablets f or 14 d ays.
Symptoms were a ssessed by q uestionnaires before rifaximin
treatment and at week 6.
Results: Hundred-fifty IBS patients were enrolled (76% female,
mean age 44 ± 16 years), of whom 106 (71%) were diagnosed
with SIBO and consequently treated with rifaximine. Rifaximine
treatment s ignificantly reduced the following symptoms as
assessed by t he s ymptom q uestionnaire: bloating (5.5 ± 2.6
before vs. 3 .6 ± 2.7 after treatment, p <0.001), flatulence (5 ±
2.7 vs. 4 ± 2.7, p = 0.015), diarrhea (2.9 ± 2.4 vs. 2 ± 2.4, p =
0.005), abdominal pain (4.8 ± 2.7 vs. 3.3 ± 2.5, p <0.001) and
resulted in improved overall well-being (3.9 ± 2.4 vs. 2.7 ± 2.3,
p <0.001). The LHBT was repeated 2-4 weeks after rifaximine
treatment in 6 5/93 (70%) patients. Eradication of SIBO was
documented in 85% of all patients (55/65).
Conclusions: The results o f our phase IV trial i ndicate that a
high proportion of IBS p atients t ested positive f or SIBO. I BS
symptoms w ere significantly diminished following a 2-week
treatment with rifaximine.