Eubiotic properties of rifaximin: Disruption of the traditional concepts in gut microbiota modulation

Abstract

Antibiotics are usually prescribed to cure infections but they also have significant modulatory effects on the gut microbiota. Several alterations of the intestinal bacterial community have been reported during antibiotic treatment, including the reduction of beneficial bacteria as well as of microbial alpha-diversity. Although after the discontinuation of antibiotic therapies it has been observed a trend towards the restoration of the original condition, the new steady state is different from the previous one, as if antibiotics induced some kind of irreversible perturbation of the gut microbial community. The poorly absorbed antibiotic rifaximin seem to be different from the other antibiotics, because it exerts non-traditional effects additional to the bactericidal/bacteriostatic activity on the gut microbiota. Rifaximin is able to reduce bacterial virulence and translocation, has anti-inflammatory properties and has been demonstrated to positively modulate the gut microbial composition. Animal models, culture studies and metagenomic analyses have demonstrated an increase in Bifidobacterium, Faecalibacterium prausnitzii and Lactobacillus abundance after rifaximin treatment, probably consequent to the induction of bacterial resistance, with no major change in the overall gut microbiota composition. Antibiotics are therefore modulators of the symbiotic relationship between the host and the gut microbiota. Specific antibiotics, such as rifaximin, can also induce eubiotic changes in the intestinal ecosystem; this additional property may represent a therapeutic advantage in specific clinical settings.

Keywords: Intestinal bacteria, Antibiotic, Rifaximin, Gut microbiota, Eubiosis, Dysbiosis, Gut microbiota modulation

Core tip: The traditional use of antibiotics in the clinical practice is to antagonize local or systemic infections. However, antibiotics induce several alterations of the gut microbiota, including the reduction of beneficial bacteria as well as of microbial diversity. Rifaximin is a non-absorbable antibiotic with broad-spectrum activity and non-traditional antimicrobial effects. Rifaximin has the potential to induce a positive modulation of the gut microbiota, favoring the growth of bacteria beneficial to the host without altering its overall composition. Therefore, rifaximin can be defined not only as an antibiotic but also as an “eubiotic”, namely a positive modulator of the gut ecosystem.