Probiotic supplementation during infancy may decrease infant gut microbial diversity and the abundance of bacteria associated with health risks

As more evidence points to the health benefits of probiotic supplementation in adults, there has been a growing interest in understanding the effects of probiotic supplementation in infants. The literature to date suggests that breast-feeding introduces some of the same beneficial bacteria to the infant gut as are present in probiotics supplements, and thus, supplementing formula-fed infants is especially of interest. However, thus far, there is no clear consensus on whether or not infant supplementation would be beneficial. The main purpose of this study was to provide further insight into the effects of probiotic intake on the microbial diversity and composition of the infant gut microbiome. Our analyses revealed that probiotic supplementation may significantly decrease infant gut microbial diversity. Although our study did not find an increase in the abundance of beneficial bacteria in the probiotic supplemented cohort, it did find an association between probiotic use and the reduction of Clostridium sensu stricto 1, Collinsella, Acinetobacter, and Erysipelatochlostridium, all of which have been linked to health risks. Additionally, the former three of these reduced genera are known to colonize breast milk, as well as the gut microbiome of breast-fed infants. Therefore, our findings suggest that probiotic supplementation may especially benefit breast-fed infants by reducing the abundance of potentially harmful bacteria genera.