Melbourne Dental School - Research Publications

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    Breastmilk influences development and composition of the oral microbiome
    Butler, CA ; Adams, GG ; Blum, J ; Byrne, SJ ; Carpenter, L ; Gussy, MG ; Calache, H ; Catmull, D ; Reynolds, EC ; Dashper, SG (TAYLOR & FRANCIS LTD, 2022-12-31)
    BACKGROUND: Human microbiomes assemble in an ordered, reproducible manner yet there is limited information about early colonisation and development of bacterial communities that constitute the oral microbiome. AIM: The aim of this study was to determine the effect of exposure to breastmilk on assembly of the infant oral microbiome during the first 20 months of life. METHODS: The oral microbiomes of 39 infants, 13 who were never breastfed and 26 who were breastfed for more than 10 months, from the longitudinal VicGeneration birth cohort study, were determined at four ages. In total, 519 bacterial taxa were identified and quantified in saliva by sequencing the V4 region of the bacterial 16S rRNA genes. RESULTS: There were significant differences in the development of the oral microbiomes of never breastfed and breastfed infants. Bacterial diversity was significantly higher in never breastfed infants at 2 months, due largely to an increased abundance of Veillonella and species from the Bacteroidetes phylum compared with breastfed infants. CONCLUSION: These differences likely reflect breastmilk playing a prebiotic role in selection of early-colonising, health-associated oral bacteria, such as the Streptococcus mitis group. The microbiomes of both groups became more heterogenous following the introduction of solid foods.
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    The Microbiome in Pancreatic Cancer-Implications for Diagnosis and Precision Bacteriophage Therapy for This Low Survival Disease.
    Kabwe, M ; Dashper, S ; Tucci, J (Frontiers Media SA, 2022)
    While the mortality rates for many cancers have decreased due to improved detection and treatments, that of pancreatic cancer remains stubbornly high. The microbiome is an important factor in the progression of many cancers. Greater understanding of the microbiome in pancreatic cancer patients, as well as its manipulation, may assist in diagnosis and treatment of this disease. In this report we reviewed studies that compared microbiome changes in pancreatic cancer patients and non-cancer patients. We then identified which bacterial genera were most increased in relative abundance across the oral, pancreatic, duodenal, and faecal tissue microbiomes. In light of these findings, we discuss the potential for utilising these bacteria as diagnostic biomarkers, as well as their potential control using precision targeting with bacteriophages, in instances where a causal oncogenic link is made.
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    Temporal development of the infant oral microbiome
    Blum, J ; Silva, M ; Byrne, SJ ; Butler, CA ; Adams, GG ; Reynolds, EC ; Dashper, SG (TAYLOR & FRANCIS LTD, 2022-11-02)
    The human oral microbiome is becoming recognized as playing roles in health and disease well beyond the oral cavity over the lifetime of the individual. The oral microbiome is hypothesized to result from specific colonization events followed by a reproducible and ordered development of complex bacterial communities. Colonization events, proliferation, succession and subsequent community development are dependent on a range of host and environmental factors, most notably the neonate diet. It is now becoming apparent that early childhood and prenatal influences can have long term effects on the development of human oral microbiomes. In this review, the temporal development of the infant human oral microbiome is examined, with the effects of prenatal and postnatal influences and the roles of specific bacteria. Dietary and environmental factors, especially breastfeeding, have a significant influence on the development of the infant oral microbiome. The evidence available regarding the roles and functions of early colonizing bacteria is still limited, and gaps in knowledge where further research is needed to elucidate these specific roles in relation to health and disease still exist.
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    Streptococcus salivarius K12 inhibits Candida albicans aggregation, biofilm formation and dimorphism
    Mokhtar, M ; Rismayuddin, NAR ; Yassim, ASM ; Ahmad, H ; Wahab, RA ; Dashper, S ; Arzmi, MH (TAYLOR & FRANCIS LTD, 2021-08-09)
    Candida albicans causes candidiasis, particularly in immunocompromised patients. Streptococcus salivarius K12 (K12) is a probiotic isolated from a healthy oral cavity. The study aimed to determine the effect of K12 on C. albicans aggregation, biofilm formation and dimorphism. C. albicans ATCC MYA-4901, acquired immunodeficiency syndrome (AIDS) isolate (ALC2), and oral cancer isolate (ALC3) and K12 were used in the study. All C. albicans strains and K12 were grown in yeast peptone dextrose agar and brain heart infusion agar, respectively, prior to aggregation, biofilm and dimorphism assays. Auto-aggregation of C. albicans MYA-4901 and ALC2 was categorised as high, while the co-aggregation of the strains was low in the presence of K12. C. albicans total cell count decreased significantly when co-cultured with K12 compared with monocultured C. albicans biofilm (p < 0.05). Inhibition of yeast-to-hyphae transition was also observed when co-cultured with K12. In conclusion, K12 inhibits C. albicans aggregation, biofilm formation and dimorphism.
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    Microbiome profiles of non-responding and responding paired periodontitis sites within the same participants following non-surgical treatment
    Byrne, SJ ; Chang, D ; Adams, GG ; Butler, CA ; Reynolds, EC ; Darby, IB ; Dashper, SG (TAYLOR & FRANCIS LTD, 2022-12-31)
    AIM: Periodontitis is a site-specific, chronic disease treated by non-surgical debridement of subgingival plaque. We aimed to determine the microbiome of sites that did not respond to this treatment (NR) compared with paired good responding (GR) sites before and after treatment. MATERIALS AND METHODS: In a longitudinal cohort study, clinical parameters of disease and biological samples were taken prior to and 3 months after treatment. Twelve NR sites from six participants were paired with GR sites within the same participant. Subgingival plaque samples were subjected to bacterial community analysis using 16S rRNA gene sequencing. RESULTS: There were no significant differences in clinical parameters and microbial communities at baseline between GR and NR sites. Bacterial communities in deep pockets were dominated by a small number of species, notably Porphyromonas gingivalis and Treponema denticola. In NR sites three months after treatment there was no significant change in bacterial composition whilst there was a collapse in the abundance of pathobionts in GR sites. CONCLUSION: NR sites were not identifiable prior to treatment by clinical or microbiological parameters. Treatment failed to disrupt pathogenic bacterial community in NR sites. Targeted suppression of particular species should be considered to initiate community collapse and aid disease resolution.
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    Taxonomy of Oral Bacteria
    Byrne, SJ ; Butler, CA ; Reynolds, EC ; Dashper, SG ; Gurtler, V ; Trevors, JT (ELSEVIER ACADEMIC PRESS INC, 2018-01-01)
    The oral cavity is a collection of diverse microenvironments, each inhabited by a community of microorganisms, the majority of which are bacteria and their phages. Given the appropriate conditions, some of these bacteria can cause destruction of the teeth or their supporting hard and soft tissues. For over 300 years microbiologists have been characterising these microbial communities, in both oral health and disease. In this chapter, we take the reader on a journey through time as we discuss the various methods that have been utilised in the characterisation of the bacteria calling the oral cavity home, and how the use of these methods has informed our understanding of oral bacterial communities and the diversity of their members.
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    The prebiotic effect of CPP-ACP sugar-free chewing gum
    Fernando, JR ; Butler, CA ; Adams, GG ; Mitchell, HL ; Dashper, SG ; Escobar, K ; Hoffmann, B ; Shen, P ; Walker, GD ; Yuan, Y ; Reynolds, C ; Reynolds, EC (ELSEVIER SCI LTD, 2019-12)
    OBJECTIVES: To determine if chewing gum containing casein phosphopeptide stabilised amorphous calcium phosphate (CPP-ACP) promoted an increase in the abundance of Streptococcus sanguinis and other species associated with dental health in supragingival plaque in a clinical study. MATERIALS AND METHODS: Nineteen participants were recruited for a three-leg cross-over, randomised, controlled clinical trial. Participants chewed a sugar-free gum with or without CPP-ACP six times daily for 20 min over two weeks. The study also involved no gum chewing (no gum) for the same two week period. Participants were randomly assigned to one of the test gums or no gum for each intervention period. Participants abstained from oral hygiene and had washout periods of two weeks between intervention periods. After each intervention period, supragingival plaque was collected and analysed for bacterial composition by sequencing the V4 variable region of the 16S rRNA gene. Data were analysed using a linear mixed model. RESULTS: The CPP-ACP gum intervention produced a significant (p < 0.01) increase in the proportions of S. sanguinis (112%), as well as the commensal species Rothia dentocariosa (127%), Corynebacterium durum (80%) and Streptococcus mitis (55%) when compared with the no gum intervention. All the species that were promoted by the CPP-ACP gum are known to possess one or both of the alkali-producing enzymes arginine deiminase and nitrate reductase. CONCLUSION: This clinical study demonstrated that chewing a sugar-free gum containing CPP-ACP promoted prebiosis by significantly increasing the proportion of S. sanguinis and other health-associated bacterial species in supragingival plaque. CLINICAL SIGNIFICANCE: Regular chewing of CPP-ACP sugar-free gum increases the proportions of health-associated commensal species in supragingival plaque to promote prebiosis and oral homeostasis.
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    Polymicrobial interactions of Candida albicans and its role in oral carcinogenesis
    Arzmi, MH ; Dashper, S ; McCullough, M (WILEY, 2019-08)
    The oral microbiome is composed of microorganisms residing in the oral cavity, which are critical components of health and disease. Disruption of the oral microbiome has been proven to influence the course of oral diseases, especially among immunocompromised patients. Oral microbiome is comprised of inter-kingdom microorganisms, including yeasts such as Candida albicans, bacteria, archaea and viruses. These microorganisms can interact synergistically, mutualistically and antagonistically, wherein the sum of these interactions dictates the composition of the oral microbiome. For instance, polymicrobial interactions can improve the ability of C albicans to form biofilm, which subsequently increases the colonisation of oral mucosa by the yeast. Polymicrobial interactions of C albicans with other members of the oral microbiome have been reported to enhance the malignant phenotype of oral cancer cells, such as the attachment to extracellular matrix molecules (ECM) and epithelial-mesenchymal transition (EMT). Polymicrobial interactions may also exacerbate an inflammatory response in oral epithelial cells, which may play a role in carcinogenesis. This review focuses on the role of polymicrobial interactions between C albicans and other oral microorganisms, including its role in promoting oral carcinogenesis.
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    Feasibility and development of a cariogenic diet scale for epidemiological research
    Amezdroz, E ; Carpenter, L ; Johnson, S ; Flood, V ; Dashper, SG ; Calache, H ; Gussy, M ; Waters, E (WILEY, 2019-05)
    BACKGROUND: Diet cariogenicity plays a major role as both a protective and risk factor in the development of early childhood caries (ECC). AIM: Develop a scale measuring the cariogenicity of foods and beverages and employ it to describe the cariogenicity of young children's diets and predict dental caries outcomes. DESIGN: Scores of cariogenicity and consumption frequency were applied to food frequency questionnaire (FFQ) collected from an Australian children's cohort study with three time-points of data. One-way ANOVA, with post hoc Tukey test compared mean cariogenic scale measured at 18 months between the subsample of children with caries classification at age 5 years. RESULTS: At 6 months, children's mean cariogenic score was 10.05, increasing to 34.18 at 12 and 50.00 at 18 months. Mean cariogenic scale score at 18 months was significantly higher in children with advanced disease at 5 years (mean scale score: 59.0 ± 15.9) compared to those that were healthy (mean score 47.7 ± 17.5, P = 0.007) or had mild-moderate disease (mean score 48.2 ± 17.3, P = 0.008). CONCLUSIONS: The cariogenic diet scale provides a useful indication of the increasing cariogenicity of children's diets with age and highlights the incorporation of discretionary choice foods and beverages into the diets of young children much earlier than nutritionally recommended.
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    Incorporation of the microencapsulated antimicrobial agent phytoncide into denture base resin
    An, S ; Judge, RB ; Wong, RH ; Arzmi, MH ; Palamara, JE ; Dashper, SG (WILEY, 2018-09)
    BACKGROUND: This study aimed to fabricate a denture base resin (DBR) containing phytoncide microcapsules (PTMCs) and determine the mechanical properties of the resin and antifungal activity. METHODS: Fifty-four heat-cured rectangular DBR specimens (64 × 10 × 3.3 ± 0.2 mm) containing nine concentrations of PTMC between 0 and 5% (wt/wt) were fabricated and subjected to a three-point bending test. A phytoncide release bioassay was developed using DBR containing 0% and 2.5% PTMCs (wt/wt) in a 24 well-plate assay with incubation of Porphyromonas gingivalis at 37 °C for 74 h. The antifungal activity of PTMCs against Candida albicans, in a pH 5.5 acidic environment was determined in a plate assay. RESULTS: Flexural strength decreased with increasing PTMC concentration from 97.58 ± 4.79 MPa for the DBR alone to 53.66 ± 2.46 MPa for DBR containing 5.0% PTMC. No release of phytoncide from the PTMCs in the DBR was detected at pH 7.4. The PTMCs had a minimal inhibitory concentration of 2.6% (wt/vol) against C. albicans at pH 5.5. CONCLUSIONS: PTMCs can be added to DBR 2.5% (wt/wt) without adversely affecting flexural strength. PTMCs released the antimicrobial agent at pH 5.5 at concentrations sufficient to inhibit the growth of the C. albicans.