Quantification of Changes in Bifidobacteria and Lactobacilli Colony-forming Units During Rifaximin Treatment and Synbiotic Gel in Healthy Volunteers.

Although the gut microbiota is generally stable, it can be influenced by antibiotic treatment. Rifaximin, which is used to treat gastrointestinal disorders, is frequently administered with probiotics to reduce the risk of dysbiosis. Lactobacillus acidophilus interacts with intestinal cells and uses prebiotic compounds. Bifidobacteria, particularly Bifidobacterium infantis ssp. lactis Bi07, is a probiotic that has been associated with beneficial effects in the gut. In vitro studies have demonstrated the superiority of agave fructans over chicory inulin. No studies have documented changes in fecal lactobacilli and bifidobacteria counts following the concomitant administration of rifaximin and synbiotic. Our objective was to evaluate changes in the CFU counts of gut bifidobacteria and lactobacilli in healthy volunteers after consumption of Synbiotic Gel, which contains Lactobacillus acidophilus NCFM, Bifidobacterium lactis Bi07, and agave inulin as a prebiotic, during 1 week of rifaximin treatment and for 4 weeks after. In a randomized, placebo-controlled, double-blind clinical trial, healthy participants without antimicrobial treatment in the previous month were randomized 1:1 in two groups (10 participants per group). The Synbiotic Gel group received 10.32 g of agave inulin as a prebiotic and 4 × 109 CFU/g of Lactobacillus acidophilus NCFM and 4 × 109 CFU/g of Bifidobacterium lactis Bi07 per day, for 5 weeks, and 200 mg rifaximin twice a day for the first week. The Placebo Gel group received placebo gel for 5 weeks and 200 mg rifaximin twice a day for the first week. Bacterial changes were estimated by quantifying CFU by microbiological assessment of feces. Five weeks later, the lactobacilli and bifidobacteria populations did not change. The detection of Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi07 in some stool samples suggests transient and partial colonization, highlighting the need for dose-response studies with this synbiotic product.