The role of genus in modulating the neonate microbiota: implications for antibiotic resistance acquisition in early life.

Resistance to antibiotics in newborns is a huge concern as their immune system is still developing, and infections and resistance acquisition in early life have short- and long-term consequences for their health. species are important commensals capable of dominating the infant gut microbiome and are known to be less prone to possess antimicrobial resistance genes than other taxa that may colonize infants. We aimed to study the association between -dominated infant gut microbiota and the antibiotic resistant gene load in neonates, and to ascertain the perinatal factors that may contribute to the antibiotic resistance acquisition. Two hundred infant fecal samples at 7 days and 1 month of age from the MAMI birth cohort were included in the study and for whom maternal-neonatal clinical records were available. Microbiota profiling was carried out by 16S rRNA amplicon sequencing, and targeted antibiotic resistance genes (ARGs) including and were quantified by qPCR. Infant microbiota clustered into two distinct groups according to their genus abundance: high and low. The main separation of groups or clusters at each time point was performed with an unsupervised non-linear algorithm of k-means partitioning to cluster data by time points based on genus relative abundance. Microbiota composition differed significantly between both groups, and specific bifidobacterial species were enriched in each cluster. Lower abundance of in the infant gut was associated with a higher load of antibiotic resistance genes. Our results highlight the relevance of genus in the early acquisition and establishment of antibiotic resistance in the gut. Further studies are needed to develop strategies to promote a healthy early colonization and fight against the spread of antibiotic resistances.