Response of Salivary Microbiota to Caries Preventative Treatment in Australian Indigenous Children

Aboriginal and Torres Strait Islander children have disproportionately poorer oral health than non-Indigenous Australian children, especially in rural communities. For three years, a once-annual caries preventative (Intervention) treatment was offered to Aboriginal and Torres Strait Islander schoolchildren of Northern Peninsula Area (NPA), Queensland, which significantly improved their oral health. Here, we examine the salivary oral microbiota of these children to understand the ecological mechanisms behind this improvement in clinical outcome. Saliva samples from children (mean age = 10 ± 2.96 years; N = 104) were used to reconstruct bacterial community composition and taxonomic abundance, with high-throughput sequencing of the V4 region of bacterial 16S ribosomal RNA gene. Microbial communities of children who received the Intervention treatment had lower taxonomic diversity than those who did not receive treatment (Shannon, p < 0.05). Moreover, the Intervention’s impact upon microbial diversity was more evident in children with active carious lesions existing at the time of saliva collection. Potential caries biomarkers were detected as the relative abundance of several microbial species, Lactobacillus salivarius, Lactobacillus reuteri, Lactobacillus gasseri, Prevotella multisaccharivorax, Parascardovia denticolens, and Mitsuokella HMT 131 were found significantly increased (p < 0.05) in children with severe caries, especially in children who did not receive the Intervention treatment. Overall, this is the first study to describe the oral microbiota from Aboriginal Australian and Torres Strait Islander peoples, simultaneously providing insight into microbial association with caries and the ecological response to treatment. Further studies are required for understanding how caries-preventative therapy induces these microbial ecological shifts and what the microbial functional repercussions of such alterations are, long-term, to further improve oral health disparities within Australia.