Salivary microbiomes of indigenous Tsimane mothers and infants are distinct despite frequent premastication.
BACKGROUND
Premastication, the transfer of pre-chewed food, is a common infant and young child feeding practice among the Tsimane, forager-horticulturalists living in the Bolivian Amazon. Research conducted primarily with Western populations has shown that infants harbor distinct oral microbiota from their mothers. Premastication, which is less common in these populations, may influence the colonization and maturation of infant oral microbiota, including via transmission of oral pathogens. We collected premasticated food and saliva samples from Tsimane mothers and infants (9-24 months of age) to test for evidence of bacterial transmission in premasticated foods and overlap in maternal and infant salivary microbiota. We extracted bacterial DNA from two premasticated food samples and 12 matched salivary samples from maternal-infant pairs. DNA sequencing was performed with MiSeq (Illumina). We evaluated maternal and infant microbial composition in terms of relative abundance of specific taxa, alpha and beta diversity, and dissimilarity distances.


RESULTS
The bacteria in saliva and premasticated food were mapped to 19 phyla and 400 genera and were dominated by Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. The oral microbial communities of Tsimane mothers and infants who frequently share premasticated food were well-separated in a non-metric multi-dimensional scaling ordination (NMDS) plot. Infant microbiotas clustered together, with weighted Unifrac distances significantly differing between mothers and infants. Infant saliva contained more Firmicutes (p< 0.01) and fewer Proteobacteria (p< 0.05) than did maternal saliva. Many genera previously associated with dental and periodontal infections, e.g.Neisseria,Gemella,Rothia,Actinomyces,Fusobacterium, andLeptotrichia, were more abundant in mothers than in infants.


CONCLUSIONS
Salivary microbiota of Tsimane infants and young children up to two years of age do not appear closely related to those of their mothers, despite frequent premastication and preliminary evidence that maternal bacteria is transmitted to premasticated foods. Infant physiology and diet may constrain colonization by maternal bacteria, including several oral pathogens.
Bioscience Division, Los Alamos National LaborataoryLos Alamos, NM, USA.
Cliff S
CS
Han
Department of Anthropology, Yale University, New Haven, CA, USA.
Melanie Ann
MA
Martin
Bioscience Division, Los Alamos National LaborataoryLos Alamos, NM, USA.
Armand E K
AEK
Dichosa
Analytics, Intelligence and Technology (A) Division, Los Alamos National Laborataory, Los Alamos, NM, USA.
Ashlynn R
AR
Daughton
Department of Medical Laboratory and Radiation Sciences, University of Vermont, Burlington, VT, USA.
Seth
S
Frietze
Department of Anthropology, University of New Mexico, Albuquerque, NM, USA.
Hillard
H
Kaplan
Department of Anthropology, University of California, Santa BarbaraSanta Barbara, CA, USA.
Michael D
MD
Gurven
Department of Emergency Medicine, University of New Mexico, Albuquerque, NM, USA.
Joe
J
Alcock
Gingivitis; Infant microbial development; Kinship; Microbe sharing; Microbial diversity; Oral disease; Oral microbiota; Premastication; Vertical transmission