Extended-spectrum b-lactamase resistance carriage effect on gut microbiota in an isolated Amerindian population

The increase of multi-resistant bacteria is a major medical issue. Many of the problems associated to antibiotic resistance depend on the spread among natural human intestinal populations of particular “high-risk” bacteria able to recruit genetic elements encoding antibiotic resistance, and possibly with high host-to-host transmission rates. In order to study the acquisition and spread of antibiotic resistance in an isolated population, we studied an Amerindian population located in a small village in the Amazon rain-forest (French Guyana) where the unique source of antibiotics is the dispensary of the village. We have tested the fecal samples from 150 individuals, representing 70% of the population, for the presence of Enterobacteria resistant to third generation cephalosporin, where we found that 8 individuals have acquired the resistance in a period of 4 years. In order to determine the possible origin of the resistances as well as the effect on the intestinal microbiota, we have studied the total and active microbiota in those eight individuals as well as in never-colonized controls, both close relatives living in the same hut and from other families. The main conclusion is that the microbiota composition is rather uniform in all the individuals analyzed, probably reflecting a similar fiber-rich diet regime. However, a specific effect of the resistance genes on the active bacteria cannot be ruled out.