Impact of Clustering Oral Symptoms in the Pathogenesis of Radiation Caries: A Systematic Review.

Radiation-related caries (RRC) is a disease with a high potential for destruction of the dentition, which impairs quality of life in head-and-neck (HN) cancer (HNC) patients who undergo radiotherapy. In light of the recently described "clustering of oral symptoms theory," the present systematic review (PROSPERO CRD42019132709) aims to assess HN and gastrointestinal (GI) symptom clusters among HNC patients and discusses how these indirect effects of cancer therapy play a pivotal role in the pathophysiology of RRC. The search was performed at PubMed, Scopus, and Embase and resulted in 11 studies that met the inclusion criteria. Data extraction was performed with respect to the presence of HN/GI symptom clusters among HNC patients. The methodological data of the studies included were assessed using the MAStARI and GRADE instruments. The most prevalent reported HN symptoms were dysphagia, xerostomia, and pain. Taste alterations and fatigue were also commonly reported by the patients. Loss of appetite and weight loss were regularly reported in the studies, as well as nausea and vomiting. The results of the present study suggest that HNC treatment generates clusters of oral symptoms, leading to dietary changes, impaired oral hygiene, enamel fragility, and a highly cariogenic oral environment, which may impact the risk for RRC. A better understanding of oral symptom clustering could be of considerable clinical significance for the oral health and quality of life of HNC patients. Therefore, contemporary protocols of RRC prevention must take this broader treatment scenario of symptom clusters such as oral side effects into account.

Changing the Paradigm of Daily Prevention to Achieve Whole Mouth Health in the 21st Century.

A comprehensive mechanical plaque control program - designed, monitored, and reinforced by dental professionals - can help patients achieve excellent oral hygiene and oral health. However, this approach to prevention is impractical for many individuals, so dental caries and periodontal disease are highly prevalent globally. Experts recently agreed that a toothpaste with fluoride and a plaque control agent can augment mechanical procedures to simultaneously prevent caries and periodontal disease. Notwithstanding this, it is timely to rethink prevention and oral health promotion. A new definition of oral health raises awareness of its different dimensions and empowers dentistry to move from treating disease to supporting prevention. In addition, a deeper understanding of the relationship between oral biofilms and the host facilitates new opportunities for disease prevention. The knowledge that health-associated biofilms help prevent establishment of pathogenic species, regulate the potentially damaging host response, and provide essential benefits to health and well-being is paramount to changing the paradigm of prevention of dental disease. Ecological approaches to biofilm control can reduce plaque sufficiently to reduce disease risk, while creating and supporting the beneficial functions of biofilms consistent with health. The knowledge that the oral soft tissues are the primary reservoir of bacteria for tooth recolonization and that reducing bacteria on soft tissues results in improved plaque control and consequently better oral health is also salient. Indeed, a toothpaste that delivers 12-hour protection to the hard and soft tissues (whole mouth protection) and multiple oral health benefits (whole mouth health) could become the future cornerstone of prevention. An innovative fluoride toothpaste with a Dual Zinc plus Arginine multi-functional therapeutic agent offers whole mouth protection against daily oral challenges and whole mouth health for the patient. Within a patient-centered preventive program, next to messaging that motivates towards improved self-care, this toothpaste empowers patients to achieve effective prevention of common oral diseases and better oral health compared to just brushing with an ordinary toothpaste.

Role of microbial biofilms in the maintenance of oral health and in the development of dental caries and periodontal diseases. Consensus report of group 1 of the Joint EFP/ORCA workshop on the boundaries between caries and periodontal disease.

BACKGROUND AND AIMS: The scope of this working group was to review (1) ecological interactions at the dental biofilm in health and disease, (2) the role of microbial communities in the pathogenesis of periodontitis and caries, and (3) the innate host response in caries and periodontal diseases. RESULTS AND CONCLUSIONS: A health-associated biofilm includes genera such as Neisseria, Streptococcus, Actinomyces, Veillonella and Granulicatella. Microorganisms associated with both caries and periodontal diseases are metabolically highly specialized and organized as multispecies microbial biofilms. Progression of these diseases involves multiple microbial interactions driven by different stressors. In caries, the exposure of dental biofilms to dietary sugars and their fermentation to organic acids results in increasing proportions of acidogenic and aciduric species. In gingivitis, plaque accumulation at the gingival margin leads to inflammation and increasing proportions of proteolytic and often obligately anaerobic species. The natural mucosal barriers and saliva are the main innate defence mechanisms against soft tissue bacterial invasion. Similarly, enamel and dentin are important hard tissue barriers to the caries process. Given that the present state of knowledge suggests that the aetiologies of caries and periodontal diseases are mutually independent, the elements of innate immunity that appear to contribute to resistance to both are somewhat coincidental.

Influence of saliva on the oral microbiota.

Saliva plays a major role in determining the composition and activity of the oral microbiota, via a variety of mechanisms. Molecules, mainly from saliva, form a conditioning film on oral surfaces, thus providing receptors for bacterial attachment. The attached cells use saliva components, such as glycoproteins, as their main source of nutrients for growth. Oral bacteria work sequentially and in a concerted manner to catabolize these structurally complex molecules. Saliva also buffers the pH in the biofilm to around neutrality, creating an environment which is conducive to the growth of many oral bacteria that provide important benefits to the host. Components of the adaptive and innate host defences are delivered by saliva, and these often function synergistically, and at sublethal concentrations, so a complex relationship develops between the host and the resident microbiota. Dysbiosis can occur rapidly if the flow of saliva is perturbed.

The effect of growth rate on pyrazinamide activity in Mycobacterium tuberculosis - insights for early bactericidal activity?

BACKGROUND: Pyrazinamide (PZA) plays an essential part in the shortened six-month tuberculosis (TB) treatment course due to its activity against slow-growing and non-replicating organisms. We tested whether PZA preferentially targets slow growing cells of Mycobacterium tuberculosis that could be representative of bacteria that remain after the initial kill with isoniazid (INH), by observing the response of either slow growing or fast growing bacilli to differing concentrations of PZA. METHODS: M. tuberculosis H37Rv was grown in continuous culture at either a constant fast growth rate (Mean Generation Time (MGT) of 23.1 h) or slow growth rate (69.3 h MGT) at a controlled dissolved oxygen tension of 10 % and a controlled acidity at pH 6.3 ± 0.1. Cultures were exposed to step-wise increases in the concentration of PZA (25 to 500 µgml(-1)) every two MGTs, and bacterial survival was measured. PZA-induced global gene expression was explored for each increase in PZA-concentration, using DNA microarray. RESULTS: At a constant pH 6.3, actively dividing mycobacteria were susceptible to PZA, with similar responses to increasing concentrations of PZA at both growth rates. Three distinct phases of drug response could be distingished for both slow growing (69.3 h MGT) and fast growing (23.1 h MGT) bacilli. A bacteriostatic phase at a low concentration of PZA was followed by a recovery period in which the culture adapted to the presence of PZA and bacteria were actively dividing in steady-state. In contrast, there was a rapid loss of viability at bactericidal concentrations. There was a notable delay in the onset of the recovery period in quickly dividing cells compared with those dividing more slowly. Fast growers and slow growers adapted to PZA-exposure via very similar mechanisms; through reduced gene expression of tRNA, 50S, and 30S ribosomal proteins. CONCLUSIONS: PZA had an equivalent level of activity against fast growing and slow growing M. tuberculosis. At both growth rates drug-tolerance to sub-lethal concentrations may have been due to reduced expression of tRNA, 50S, and 30S ribosomal proteins. The findings from this study show that PZA has utility against more than one phenotypic sub-population of bacilli and could be re-assessed for its early bactericidal activity, in combination with other drugs, during TB treatment.

Hemin availability induces coordinated DNA methylation and gene expression changes in Porphyromonas gingivalis.

Periodontal disease is a chronic inflammatory disease in which the oral pathogen Porphyromonas gingivalis plays an important role. Porphyromonas gingivalis expresses virulence determinants in response to higher hemin concentrations, but the underlying regulatory processes remain unclear. Bacterial DNA methylation has the potential to fulfil this mechanistic role. We characterized the methylome of P. gingivalis, and compared its variation to transcriptome changes in response to hemin availability. Porphyromonas gingivalis W50 was grown in chemostat continuous culture with excess or limited hemin, prior to whole-methylome and transcriptome profiling using Nanopore and Illumina RNA-Seq. DNA methylation was quantified for Dam/Dcm motifs and all-context N6-methyladenine (6mA) and 5-methylcytosine (5mC). Of all 1,992 genes analyzed, 161 and 268 were respectively over- and under-expressed with excess hemin. Notably, we detected differential DNA methylation signatures for the Dam "GATC" motif and both all-context 6mA and 5mC in response to hemin availability. Joint analyses identified a subset of coordinated changes in gene expression, 6mA, and 5mC methylation that target genes involved in lactate utilization and ABC transporters. The results identify altered methylation and expression responses to hemin availability in P. gingivalis, with insights into mechanisms regulating its virulence in periodontal disease. IMPORTANCE DNA methylation has important roles in bacteria, including in the regulation of transcription. Porphyromonas gingivalis, an oral pathogen in periodontitis, exhibits well-established gene expression changes in response to hemin availability. However, the regulatory processes underlying these effects remain unknown. We profiled the novel P. gingivalis epigenome, and assessed epigenetic and transcriptome variation under limited and excess hemin conditions. As expected, multiple gene expression changes were detected in response to limited and excess hemin that reflect health and disease, respectively. Notably, we also detected differential DNA methylation signatures for the Dam "GATC" motif and both all-context 6mA and 5mC in response to hemin. Joint analyses identified coordinated changes in gene expression, 6mA, and 5mC methylation that target genes involved in lactate utilization and ABC transporters. The results identify novel regulatory processes underlying the mechanism of hemin regulated gene expression in P. gingivalis, with phenotypic impacts on its virulence in periodontal disease.

Molecular basis for avirulence of spontaneous variants of Porphyromonas gingivalis: Genomic analysis of strains W50, BE1 and BR1.

The periodontal pathogen Porphyromonas gingivalis is genetically heterogeneous. However, the spontaneous generation of phenotypically different sub-strains has also been reported. McKee et al. (1988) cultured P. gingivalis W50 in a chemostat during investigations into the growth and properties of this bacterium. Cell viability on blood agar plates revealed two types of non-pigmenting variants, W50 beige (BE1), and W50 brown (BR1), in samples grown in a high-hemin medium after day 7, and the population of these variants increased to approximately 25% of the total counts by day 21. W50, BE1 and BR1 had phenotypic alterations in pigmentation, reduced protease activity and haemagglutination and susceptibility to complement killing. Furthermore, the variants exhibited significant attenuation in a mouse model of virulence. Other investigators showed that in BE1, the predominant extracellular Arg-gingipain was RgpB, and no reaction with an A-lipopolysaccharide-specific MAb 1B5 (Collinson et al., 1998; Slaney et al., 2006). In order to determine the genetic basis for these phenotypic properties, we performed hybrid DNA sequence long reads using Oxford Nanopore and the short paired-end DNA sequence reads of Illumina HiSeq platforms to generate closed circular genomes of the parent and variants. Comparative analysis indicated loss of intact kgp in the 20 kb region of the hagA-kgp locus in the two variants BE1 and BR1. Deletions in hagA led to smaller open reading frames in the variants, and BR1 had incurred a major chromosomal DNA inversion. Additional minor changes to the genomes of both variants were also observed. Given the importance of Kgp and HagA to protease activity and haemagglutination, respectively, in this bacterium, genomic changes at this locus may account for most of the phenotypic alterations of the variants. The homologous and repetitive nature of hagA and kgp and the features at the inverted junctions are indicative of specific and stable homologous recombination events, which may underlie the genetic heterogeneity of this species.

Optimization of conditions for in vitro modeling of subgingival normobiosis and dysbiosis.

Modeling subgingival microbiome in health and disease is key to identifying the drivers of dysbiosis and to studying microbiome modulation. Here, we optimize growth conditions of our previously described in vitro subgingival microbiome model. Subgingival plaque samples from healthy and periodontitis subjects were used as inocula to grow normobiotic and dysbiotic microbiomes in MBEC assay plates. Saliva supplemented with 1%, 2%, 3.5%, or 5% (v/v) heat-inactivated human serum was used as a growth medium under shaking or non-shaking conditions. The microbiomes were harvested at 4, 7, 10 or 13 days of growth (384 microbiomes in total) and analyzed by 16S rRNA gene sequencing. Biomass significantly increased as a function of serum concentration and incubation period. Independent of growth conditions, the health- and periodontitis-derived microbiomes clustered separately with their respective inocula. Species richness/diversity slightly increased with time but was adversely affected by higher serum concentrations especially in the periodontitis-derived microbiomes. Microbial dysbiosis increased with time and serum concentration. Porphyromonas and Alloprevotella were substantially enriched in higher serum concentrations at the expense of Streptococcus, Fusobacterium and Prevotella. An increase in Porphyromonas, Bacteroides and Mogibacterium accompanied by a decrease in Prevotella, Catonella, and Gemella were the most prominent changes over time. Shaking had only minor effects. Overall, the health-derived microbiomes grown for 4 days in 1% serum, and periodontitis-derived microbiomes grown for 7 days in 3.5%-5% serum were the most similar to the respective inocula. In conclusion, normobiotic and dysbiostic subgingival microbiomes can be grown reproducibly in saliva supplemented with serum, but time and serum concentration need to be adjusted differently for the health and periodontitis-derived microbiomes to maximize similarity to in vivo inocula. The optimized model could be used to identify drivers of dysbiosis, and to evaluate interventions such as microbiome modulators.

Temperature-dependent modulation of Porphyromonas gingivalis lipid A structure and interaction with the innate host defenses.

Lipid A structure is a critical determinant of the interaction between pathogens and the innate immune system. Previously, we demonstrated the presence of non- and monophosphorylated tetra-acylated lipid A structures in the outer membrane of Porphyromonas gingivalis, an agent of human periodontal disease. These modifications to lipid A structure lead to evasion and suppression of innate defenses mediated by Toll-like receptor 4 (TLR4) and cationic antimicrobial peptides. In this investigation, we examined the influence of growth temperature on P. gingivalis lipid A structure and recognition by TLR4 as an example of an environmental influence which is known to vary between healthy and diseased sites in the periodontium. We demonstrate that P. gingivalis grown at a normal body temperature produces mainly nonphosphorylated and monophosphorylated tetra-acylated lipid A structures, whereas bacteria grown at 39°C and 41°C intended to mimic increasing levels of inflammation, producing increasing proportions of monophosphorylated, penta-acylated lipid A. The temperature-dependent alteration in lipid A renders the bacterium significantly more potent for activating TLR4 and more susceptible to killing by ß-defensins 2 and 3. This is the first report of a lipid A remodeling system linked to temperature shifts associated with a deregulated inflammatory response. Temperature elevation at sites of inflammation in the periodontium may be a significant environmental regulator of the lipid A modification systems of P. gingivalis, which will influence the interaction of this organism with the innate host defense.

How is the development of dental biofilms influenced by the host?

BACKGROUND: The host provides environmental conditions that support diverse communities of microorganisms on all environmentally-exposed surfaces of the body. MATERIALS AND METHODS: To review the literature to determine which properties of the host substantially influence the development of dental biofilms. RESULTS: The mouth facilitates the growth of a characteristic resident microbiota. The composition of the oral microbiota is influenced by temperature, pH, and atmosphere, as well as by the host defences and host genetics. In addition, the host supplies endogenous nutrients and a variety of surfaces for biofilm formation. In health, the resident oral microbiota forms a symbiotic relationship with the host, regulated by active host-microbe cross talk. This resident microbiota is sensitive to perturbations in the host environment, especially to changes in nutrient supply and pH, so that previously minor components of the microbiota can become more competitive (and vice versa), resulting in reorganization of biofilm community structure. CONCLUSION: The host environment dictates the composition and gene expression of the resident microbiota. Changes in oral environmental conditions can disrupt the normal symbiotic relationship between the host and its resident microbes, and increase the risk of disease.

Understanding dental caries as a non-communicable disease.

The recent developments in the science underpinning our knowledge of both the initiation of dental caries and the subsequent behaviour of lesions over time gives us a solid base to understand caries differently. Advances in understanding the human and oral microbiome have come in parallel with the recognition of the importance of balancing protective and pathological risk factors. Caries prevention and management is now about controlling risk factors to maintain a balanced intraoral biofilm ecology that guards against a continuing low pH driven by the frequent consumption of sugars. Thus, caries control is no longer about attempts at eradicating any specific microorganism. Further, the present knowledge leads to the classification of dental caries as a non-communicable disease (NCD), which is vitally important from a policy perspective (both globally and at the country level). Caries shares similar risk factors with other chronic/systemic diseases, which provides opportunities for developing common prevention strategies and promoting health equity through action on the social determinants of health. So, preventing and controlling caries should be integrated across the so-called upstream, midstream and downstream levels and these activities can also help to control other NCDs.

A cross-species interaction with a symbiotic commensal enables cell-density-dependent growth and in vivo virulence of an oral pathogen.

Recent studies describe in detail the shifts in composition of human-associated polymicrobial communities from health to disease. However, the specific processes that drive the colonization and overgrowth of pathogens within these communities remain incompletely understood. We used in vitro culture systems and a disease-relevant mouse model to show that population size, which determines the availability of an endogenous diffusible small molecule, limits the growth, colonization, and in vivo virulence of the human oral pathogen Porphyromonas gingivalis. This bacterial pathogen overcomes the requirement for an endogenous cue by utilizing a cell-density dependent, growth-promoting, soluble molecule provided by the symbiotic early colonizer Veillonella parvula, but not produced by other commensals tested. Our work shows that exchange of cell-density-dependent diffusible cues between specific early and late colonizing species in a polymicrobial community drives microbial successions, pathogen colonization and disease development, representing a target process for manipulation of the microbiome towards the healthy state.

Immunomodulatory streptococci that inhibit CXCL8 secretion and NFκB activation are common members of the oral microbiota.

Introduction. Oral tissues are generally homeostatic despite exposure to many potential inflammatory agents including the resident microbiota. This requires the balancing of inflammation by regulatory mechanisms and/or anti-inflammatory commensal bacteria. Thus, the levels of anti-inflammatory commensal bacteria in resident populations may be critical in maintaining this homeostatic balance.Hypothesis/Gap Statement. The incidence of immunosuppressive streptococci in the oral cavity is not well established. Determining the proportion of these organisms and the mechanisms involved may help to understand host-microbe homeostasis and inform development of probiotics or prebiotics in the maintenance of oral health.Aim. To determine the incidence and potential modes of action of immunosuppressive capacity in resident oral streptococci.Methodology. Supragingival plaque was collected from five healthy participants and supragingival and subgingival plaque from five with gingivitis. Twenty streptococci from each sample were co-cultured with epithelial cells±flagellin or LL-37. CXCL8 secretion was detected by ELISA, induction of cytotoxicity in human epithelial cells by lactate dehydrogenase release and NFκB-activation using a reporter cell line. Bacterial identification was achieved through partial 16S rRNA gene sequencing and next-generation sequencing.Results. CXCL8 secretion was inhibited by 94/300 isolates. Immunosuppressive isolates were detected in supragingival plaque from healthy (4/5) and gingivitis (4/5) samples, and in 2/5 subgingival (gingivitis) plaque samples. Most were Streptococcus mitis/oralis. Seventeen representative immunosuppressive isolates all inhibited NFκB activation. The immunosuppressive mechanism was strain specific, often mediated by ultra-violet light-labile factors, whilst bacterial viability was essential in certain species.Conclusion. Many streptococci isolated from plaque suppressed epithelial cell CXCL8 secretion, via inhibition of NFκB. This phenomenon may play an important role in oral host-microbe homeostasis.

Characterization of the Infant Immune System and the Influence and Immunogenicity of BCG Vaccination in Infant and Adult Rhesus Macaques.

In many countries where tuberculosis (TB) is endemic, the Bacillus Calmette-Guérin (BCG) vaccine is given as close to birth as possible to protect infants and children from severe forms of TB. However, BCG has variable efficacy and is not as effective against adult pulmonary TB. At present, most animal models used to study novel TB vaccine candidates rely on the use of adult animals. Human studies show that the infant immune system is different to that of an adult. Understanding how the phenotypic profile and functional ability of the immature host immune system compares to that of a mature adult, together with the subsequent BCG immune response, is critical to ensuring that new TB vaccines are tested in the most appropriate models. BCG-specific immune responses were detected in macaques vaccinated within a week of birth from six weeks after immunization indicating that neonatal macaques are able to generate a functional cellular response to the vaccine. However, the responses measured were significantly lower than those typically observed following BCG vaccination in adult rhesus macaques and infant profiles were skewed towards the activation and attraction of macrophages and monocytes and the synthesis in addition to release of pro-inflammatory cytokines such as IL-1, IL-6 and TNF-α. The frequency of specific immune cell populations changed significantly through the first three years of life as the infants developed into young adult macaques. Notably, the CD4:CD8 ratio significantly declined as the macaques aged due to a significant decrease in the proportion of CD4+ T-cells relative to a significant increase in CD8+ T-cells. Also, the frequency of both CD4+ and CD8+ T-cells expressing the memory marker CD95, and memory subset populations including effector memory, central memory and stem cell memory, increased significantly as animals matured. Infant macaques, vaccinated with BCG within a week of birth, possessed a significantly higher frequency of CD14+ classical monocytes and granulocytes which remained different throughout the first three years of life compared to unvaccinated age matched animals. These findings, along with the increase in monokines following vaccination in infants, may provide an insight into the mechanism by which vaccination with BCG is able to provide non-specific immunity against non-mycobacterial organisms.

High-dose Mycobacterium tuberculosis aerosol challenge cannot overcome BCG-induced protection in Chinese origin cynomolgus macaques; implications of natural resistance for vaccine evaluation.

This study describes the use of cynomolgus macaques of Chinese origin (CCM) to evaluate the efficacy and immunogenicity of the BCG vaccine against high dose aerosol Mycobacterium tuberculosis challenge. Progressive disease developed in three of the unvaccinated animals within 10 weeks of challenge, whereas all six vaccinated animals controlled disease for 26 weeks. Three unvaccinated animals limited disease progression, highlighting the intrinsic ability of this macaque species to control disease in comparison to macaques of other species and genotypes. Low levels of IFNγ were induced by BCG vaccination in CCM suggesting that IFNγ alone does not provide a sufficiently sensitive biomarker of vaccination in this model. An early response after challenge, together with the natural bias towards terminal effector memory T-cell populations and the contribution of monocytes appears to enhance the ability of CCM to naturally control infection. The high dose aerosol challenge model of CCM has value for examination of the host immune system to characterise control of infection which would influence future vaccine design. Although it may not be the preferred platform for the assessment of prophylactic vaccine candidates, the model could be well suited for testing post-exposure vaccination strategies and drug evaluation studies.

Dental plaque as a biofilm: the significance of pH in health and caries.

Dental plaque is an example of a biofilm; its presence is natural and it supports the host in its defense against invading microbes. In health, the microbial composition of dental plaque is diverse and remains relatively stable over time (microbial homeostasis). The predominant microorganisms prefer host molecules (eg, salivary mucins) and a neutral pH for growth. Under certain circumstances, this microbial homeostasis can break down and diseases such as caries can occur. In dental caries, there is a shift toward increased proportions of acid-producing and acid-tolerating species, such as mutans streptococci and Lactobacilli, although other species with relevant traits can participate in demineralization. Strategies to control caries include effective oral hygiene practices to reduce biofilm development, and adoption of a low-sugar diet to restrict periods of acidic challenge to teeth. These conventional approaches also should be augmented by interference with the factors that enable the cariogenic bacteria to outcompete the organisms associated with health. Evidence suggests that regular conditions of low pH in plaque select for mutans streptococci and Lactobacilli. Therefore, the suppression of sugar catabolism and acid production by the use of metabolic inhibitors in oral care products, the consumption of nonfermentable sweeteners in snacks, the stimulation of saliva flow, and/or other strategies that maintain supragingival plaque at a pH around neutrality will assist in the maintenance of microbial homeostasis in plaque.

Applications of the oral microbiome in personalized dentistry.

OBJECTIVE: In the era of personalized medicine, it is imperative that oral health is integrated into this concept. The oral cavity fosters a highly individualized microbiome that has evolved to promote oral health, and which exists in a dynamic balance with the host. Microecological changes to the biology of the mouth [e.g. in the host diet and lifestyle, or status of the immune system] may drive deleterious shifts in the composition or metabolic activity of the oral microbiome ['dysbiosis']. This review aims to explore how knowledge of the oral microbiome may be utilized for personalized dentistry at the point-of-care. DESIGN: This is a comprehensive narrative review of the literature, summarizing the perspectives of the authors. RESULTS: The huge increase in recent knowledge on the ecology and microbiology of the oral cavity generated by 'OMIC' technologies may indeed be clinically translated to support patient care, in terms of prevention, monitoring, risk classification or early diagnosis. The identified clinical applications may not only include dental caries and periodontal disease, but also dental implants and orthodontics. Population-based applications may include systemic health, pregnancy and elderly populations. CONCLUSIONS: Applications of selected oral microbiome and host-related biochemical parameters [e.g. the saliva proteome] for personalized dentistry can be customized for different clinical applications or individual populations, at point-of-care hubs.

Differences in monocyte: lymphocyte ratio and Tuberculosis disease progression in genetically distinct populations of macaques.

Monocyte:lymphocyte ratio (M:L) has been identified as a risk factor in development of TB disease in children and those undergoing treatment for HIV in co-infected individuals. Retrospective analysis was performed using M:L data collected from TB modelling studies performed in Rhesus macaques of Indian genotype (RM), cynomolgus macaque of Chinese genotype (CCM) and cynomolgus macaque of Mauritian genotype (MCM), which found that the more susceptible populations (RM and MCM) had higher M:L ratios than the least susceptible population (CCM). Following Mycobacterium tuberculosis exposure, significant increases in M:L ratio were observed in susceptible RM and MCM within 12 weeks of TB infection, whereas M:L in CCM remained stable, suggesting that changes in M:L ratio may also act as a biomarker of TB disease progression. The frequency of PPD-specific interferon gamma (IFNγ) secreting cells (SFU) were compared, with the more susceptible macaque populations showing an association between M:L and IFNγ SFU frequency. Investigation of the genes associated with monocyte-derived antigen presenting cells revealed differences between RM and CCM, highlighting differences in their monocyte populations, as well as overall M:L ratio. Differences in M:L ratio between macaque populations could be used to explore immunological mechanisms in susceptible populations that would complement human population studies.

Transcriptional responses of Mycobacterium tuberculosis exposed to adverse conditions in vitro.

Mycobacterium tuberculosis encounters a range of stimuli in the host. Understanding the environmental cues that initiate the transcriptional response of M. tuberculosis, which enable the bacterium to replicate and/or survive in the host, will provide markers that are specific to different stages of disease, further refining the search for improved treatments and vaccines. Studying M. tuberculosis gene expression in vivo is technically challenging and more amenable in vitro experiments are being used to aid interpretation and to dissect the signals that are responsible for controlling subsets of genes. Key parameters that affect the growth of a pathogen in the host include nutrient status, environmental pH, oxygen availability, and host defences. Studying gene expression, pathogenicity, and physiology of M. tuberculosis that has been exposed to these relevant host conditions in vitro will further increase our understanding of the virulence factors that M. tuberculosis requires to establish disease. Complementary information obtained by metabolic flux analysis, proteomics, and regulatory networks analysis will enable a clearer picture of how transcriptional responses translate to changes in the metabolome and physiology of the organism.