Human pre-colostrum: potential role as a source of bacteria to the infant mouth

Abstract

[Background] Oral bacteria in human milk are usually considered a contamination from the infant oral cavity during breastfeeding but the influence of milk on initial acquisition of oral microbiota has not been investigated. [Objective] To investigate the composition of the microbiota of maternal pre-colostrum produced before birth and to study its potential as a source of bacteria to the infant mouth. [Methods] Pre-colostrum and infant saliva were collected from 19 mother-infant pairs. Microbiomes were analyzed (V3-V4 regions of 16S rDNA) in an Illumina platform. Bacteria were isolated and identified by MALDI-TOF. Whole-genome sequencing was performed on those isolates that seemed to be shared in both samples from the same mother-infant pair. [Results] Certain bacterial groups (mainly Streptococcus and Staphylococcus) were shared between precolostrum and infant salivary samples. In 13 pairs, at least one isolate from the same species was recovered from pre-colostrum and salivary samples. Globally, 8 out of 10 fully sequenced strain pairs were >99.9% identical at the nucleotide level. [Conclusions] The presence of oral bacteria in colostrum before contact with the newborn indicates that they are not a contamination from the infant and suggests that at least some oral bacteria colonize the infant’s oral cavity through transmission through human milk.