Sharing of bacterial strains between pre-colostrum and infant saliva: culture independent and culture dependent approaches

Trabajo presentado en el IX Workshop de la Sociedad Española de Probióticos y Prebióticos (SEPyP), celebrado en Zaragoza (España) el 15 y 16 de febrero de 2018[Introduction] The infant oral microbiome might impact the infant gut microbiome establishment providing the first commensals that will reach the infant gut (1). Besides, human milk represents a source of bacteria for the initial establishment of the oral (and gut) microbiomes in the breastfed infant (2,3) although little is known on the origin of the human milk microbiome and its impact on the infant oral microbiome. [Objectives] To investigate the maternal precolostrum and infant oral microbiomes to identify bacterial species (strains) shared in the maternal-infant dyad. [Methods] 16S rRNA sequencing microbiome profiling was performed on maternal precolostrum and infant saliva collected from 19 mother-infant pairs. Bacteria were cultured, isolated and identified by MALDI-TOF. RAPD-PCr and full genome sequencing was performed on those isolates that, belonging to the same species, were isolated from both the maternal and infant samples in the same mother-infant pair. [Results] Maternal precolostrum and infant salivary microbiomes significantly differed, although certain taxa were consistently shared, Streptococcus and Staphylococcus spp. being the most abundant. In 13 pairs, at least one isolate from the same species was recovered from both sample types. From those, isolates obtained from precolostrum and infant saliva in 8 of the pairs could not be distinguised by RAPD-PCR profiling. 8 out of 10 fully sequenced isolate pairs were > 99.9% identical at nucleotide level, thus suggesting the sharing of bacteria at strain level between precolostrum and infant oral microbiomes. [Conclusions] The presence of oral bacteria in precolostrum, before contact with the newborn, indicates that they are not a contamination from the infant gut and suggests that at least some oral bacteria colonize the infant's oral cavity through transmission through breastmilk.Peer reviewe