Sharing of bacterial strains between maternal precolostrum and infant saliva: culture independent and culture dependent approaches

Abstract

[Background] The infant oral microbiome exerts an important role in the establishment of the infant gut microbiome since it contains the first commensals that will reach and stably colonize the infant gut, but it also influences the dental health of the adult. In this context, human milk represents a source of bacteria for the initial establishment of the oral (and gut) microbiomes in the breastfed infant although little is known on the specific mechanisms that condition the early establishment and development of the infant oral microbiomes. [Objectives] To investigate the maternal colostrum and infant oral microbiomes to identify bacterial species (strains) shared in the maternal-infant dyad. [Methods] Maternal pre-colostrum and infant saliva were collected from 19 mother-infant pairs and their microbiomes were analyzed through 16S rRNA metagenomics sequencing. Bacteria were also cultured, isolated and identified by MALDI-TOF. RAPD-PCR was performed on those isolates that, belonging to the same species, were shared in the maternal and infant samples of the same pair. [Conclusions] Maternal pre-colostrum and infant salivary microbiomes were significantly different from each other, although certain groups were consistently shared between both sample types. Streptococcus and Staphylococcus spp were the most abundant groups in all samples. In 13 pairs, at least one isolate from the same species was recovered from the colostrum and the salivary sample. From those, the isolates obtained from colostrum and infant saliva in 8 of the pairs could not be distinguished by RAPD-PCR profiling, thus suggesting the sharing of bacteria at strain level between milk and infant oral microbiomes.