The surfaces of the oral cavity provide a complex environmental niche where biofilms composed of anaerobic and aerobic bacterial species, fungi, and viruses intermingle to provide oral health or disease. Some of the biofilms occurring at oral surfaces include periodontitis, gingivitis, implantitis, mucositis, endodontic infection, and the most common oral infection, dental caries (cavities). Dental caries occur through acidification of the local microenvironment by biofilm-embedded bacteria at the tooth enamel surface and acid dependent enamel dissolution. Caries in the children has been a major global public health issue due to its high cost to treat and severe infectious outcomes if left untreated. Although culture-based studies have identified a number of cariogenic bacterial species such as mutans streptococci and their lactic acid production to be the major etiological agent in caries development, the global gene expression patterns have yet to be determined. The purpose of this study was to utilize RNASeq to compare microbial transcriptomes in dental plaque from caries active sites and compare these to healthy sites in children. Seven paired clinical dental plaque samples were obtained from caries sites (n = 7) and non-caries sites (n = 7) in children seen at the University of Maryland, School of Dentistry. Two additional plaque samples were collected from caries free children using the same criteria. Total RNA was extracted, depleted of rRNA, and used in the construction of RNASeq libraries. The Illumina MiSeq platform was used for RNASeq sequencing and analysis was then performed using Statistical Analysis of Metagenomic (and other) Profiles (STAMP) v2(34). A two-sided White's non-parametric t-test with a Storey's FDR multiple test correction was used to test for statistical significance. Our results showed the significant domination of Fusobacteria in caries plaque versus healthy plaque. Surprisingly, Leptotrichia spp. and not streptococcal species were found to be overexpressed in caries plaque while Actinomyces dominated the plaque samples from healthy sites in all subjects. The metabolic pathways producing acetate was to be found up-regulated five fold in plaque from caries sites versus plaque from healthy sites. A non-streptococcal bacterial species and lactic acid-independent cariogenic mechanism may be the major factors in childhood caries formation. However, further research using a larger sample size will be needed to confirm these findings.

Microbial transcriptomic analysis of cariogenic bacterial species at enamel surfaces in a pediatric population

254th National Meeting (2017)

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