Abstract/Summary

The oral microbiome can exert an effect on human health and well being.Equilibrium between bacteria and host must be met in order to confer benefits to each. This interaction has raised questions as to the importance of microbial functions in health and disease. To date, research has focused on the bacterial colonization of the oral cavity and the detrimental health effects of this colonisation. However, few studies have investigated the effects of naturally occurring compounds and potential oral prebiotics on the oral microbiome structure and function (including bacterial metabolism). The primary purpose of this project looked at what determined a putative healthy state in the mouth to evaluate means to manipulate and maintain a healthy status. Enrichment cultivations were run with samples from 3 healthy volunteers across 7 oral sites in order to determine the effect of mucin breakdown on bacterial metabolites and what environmental conditions influence mucin breakdown (aerobic/anaerobic). Bacterial diversity was found to follow a cyclic manner between simple and complex profiles, with greater diversity seen under anaerobic conditions and for 48 hr samples. Further, samples taken from sites in contact with teeth or tongue displayed the greatest bacterial banding patterns. Dominant bands were noted to run across gels from all enrichment suggesting the presence of potential primary mucin degraders. Major metabolites produced during mucin enrichments were the SCFA acetate and butyrate,in conjunction with detection of the amino acids threonine, serine and proline. The highest rates of SCFA production (acetate) were seen for anaerobic samples. The results of this study suggest that mucin degradation involves the metabolism of a consortium of bacteria. In order to determine the effect of mucins on the oral micro biota in vivo their stimulation was tested in conjunction with potential oral prebiotics. These prebiotics (lactose, FOS, and cGMP) were mixed with xylitol and administered either in mouthwashes or chewing gums to healthy volunteers over a course of separate 4 weeks human trials. Saliva (unstimulated and stimulated) and dental plaque samples were taken and subjected to high resolution analytical and metabolomic techniques to monitor profiles of microbiome, metabolites and mucins. Both vehicles of administration were able to modulate the oral micro biota as well as affecting SCFA metabolism. In the mouthwash trial a decrease of Fusobacterium was noted across all treatments while increases of Veillonella were seen in all treatments but cGMP. While in the gum trial Prevotella decreased across all treatments but FOS. Further, metabolism products related to SCFAs mainly acetate. It was noted that the lactose-supplemented mouthwash lead to the greatest decreases in acid production, while in the gum trial lactose and cGMP treatments lead to the greatest acid production. Throughout both trials it was noted that mucin concentrations differed by saliva type. Mucin subtype MUC 5 abundance was greater in unstimulated saliva while, subtype MUC 7 was greater in stimulated saliva samples. It was noted for both trials that FOS- and cGMP-supplementations increased potentially pathogenic bacterial populations (Fusobacterium and Veillonella) and undesirable SCFA concentrations (acetate, lactate). Lactose-supplementation was able to modulate the oral ecosystem by increasing potentially beneficial bacteria (Streptococcus). Taken together these studies have provided insight into how potential oral prebiotics can affect the oral cavity due to their metabolism and have examined the effects on mucin stimulation and their interactions with bacterial populations.