Galacto-oligosaccharides to counter the side effects of antibiotic treatments

Antibiotic treatments are known to disturb the composition and metabolic activity of the human gut microbiota and, therefore, may lead to gut disorders. In this thesis, it was investigated whether and by which mechanisms galacto-oligosaccharides (GOS), a prebiotic known to stimulate the growth of bifidobacteria and to positively influence human health, may counter the  negative effects of antibiotics on the microbiota.

First, a high throughput approach combining the in vitro fermentation screening platform with a phylogenetic microarray read-outs was shown to be reliable to simultaneously analyse the effects of several often-used antibiotics on the intestinal microbiota. Then, using the same approach, the recovery of the composition and metabolic activity of the microbiota treated with four selected antibiotics upon GOS addition was shown to be antibiotic and dose dependant. The addition of GOS to an amoxicillin (AMX)-treated microbiota was considered successful as, after a decrease of the levelofBifidobacterium species, the recovery of mainly Bifidobacterium longum, was observed. The growth of bifidobacteria and the production of the beneficial butyrate tended to be higher upon addition of small GOS (dimers-trimers) than upon large GOS in non-treated microbiota (tetramers to hexamers). On the contrary in AMX-treated microbiota, the growth of bifidobacteria and production of butyrate tented to be higher upon addition of large GOS than upon addition of small GOS. The positive results of GOS on AMX-treated microbiota during in vitro experiments were evidenced in a double-blind randomized parallel intervention study involving 12 healthy adults.

Overall, the addition of GOS, especially the large oligosaccharides, allowed the recovery of B. longum and, subsequently, stimulated the activity of the microbiota through cross-feeding after an AMX treatment.