Melbourne Dental School - Research Publications
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ItemComplementation in trans of Porphyromonas gingivalis Lipopolysaccharide Biosynthetic Mutants Demonstrates Lipopolysaccharide Exchange(American Society for Microbiology, 2021-04-21)Porphyromonas gingivalis, a bacterial pathogen contributing to human periodontitis, exports and anchors cargo proteins to its surface, enabling the production of black pigmentation using a type IX secretion system (T9SS) and conjugation to anionic lipopolysaccharide (A-LPS). To determine whether T9SS components need to be assembled in situ for correct secretion and A-LPS modification of cargo proteins, combinations of nonpigmented mutants lacking A-LPS or a T9SS component were mixed to investigate in trans complementation. Reacquisition of pigmentation occurred only between an A-LPS mutant and a T9SS mutant, which coincided with A-LPS modification of cargo proteins detected by Western blotting and coimmunoprecipitation/quantitative mass spectrometry. Complementation also occurred using an A-LPS mutant mixed with outer membrane vesicles (OMVs) or purified A-LPS. Fluorescence experiments demonstrated that OMVs can fuse with and transfer lipid to P. gingivalis, leading to the conclusion that complementation of T9SS function occurred through A-LPS transfer between cells. None of the two-strain crosses involving only the five T9SS OM component mutants produced black pigmentation, implying that the OM proteins cannot be transferred in a manner that restores function and surface pigmentation, and hence, a more ordered temporal in situ assembly of T9SS components may be required. Our results show that LPS can be transferred between cells or between cells and OMVs to complement deficiencies in LPS biosynthesis and hemin-related pigmentation to reveal a potentially new mechanism by which the oral microbial community is modulated to produce clinical consequences in the human host. IMPORTANCE: Porphyromonas gingivalis is a keystone pathogen contributing to periodontitis in humans, leading to tooth loss. The oral microbiota is essential in this pathogenic process and changes from predominantly Gram-positive (health) to predominantly Gram-negative (disease) species. P. gingivalis uses its type IX secretion system (T9SS) to secrete and conjugate virulence proteins to anionic lipopolysaccharide (A-LPS). This study investigated whether components of this secretion system could be complemented and found that it was possible for A-LPS biosynthetic mutants to be complemented in trans both by strains that had the A-LPS on the cell surface and by exogenous sources of A-LPS. This is the first known example of LPS exchange in a human bacterial pathogen which causes disease through complex microbiota-host interactions.
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ItemIADR 100 Years On: Driving Science, Engagement, and Globalization Post COVID-19(SAGE PUBLICATIONS INC, 2021-12)
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ItemSocial practice theory: An innovative approach to considering preschool children's poor oral health(WILEY, 2021-08)Oral disease in early childhood is highly prevalent and costly and impacts on the child and family with significant societal costs. Current approaches have largely failed to improve young children's oral health. This paper proposes a different approach to conceptualize poor oral health in preschool children (0-5 years) using social practices. Social practice theory offers an innovative perspective to understanding oral health by shifting emphasis away from the individual and onto how practical, social and material arrangements around the oral health of preschool children exist, change or become embedded in the social structures they inhabit. This novel approach contributes to the growing theoretical understanding in this area and has the potential to offer insights into the problem and ways it might be addressed.
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ItemPerceptions of oral health education and practice among nursing students in Malaysia and Australia(WILEY, 2021-05)OBJECTIVE: Representing the largest proportion of healthcare workers, nurses play a significant role in oral health (OH) maintenance as part of a larger effort to promote holistic patient care. The study aims to determine nursing students' perceptions of OH education and practice in Malaysian and Australian nursing schools. MATERIALS AND METHODS: A self-administered questionnaire (content- and face-validated) survey was undertaken, classroom style, amongst final-year nursing students from selected Malaysian (n = 122, Response rate=97.6%) and Australian (n = 299, Response rate=54.7%) institutions. Quantitative data were analysed via Statistical Package for Social Science software (Chi-square and Fisher's exact tests, p ā¤ 0.01). RESULTS: Significantly more Malaysian nursing students, compared to those in Australia, reported having encountered patients with OH issues (98.4% vs. 82.9%), namely halitosis (87.7% vs. 62.2%), oral ulcers (63.1% vs. 41.1%), oral/dental trauma (36.9% vs. 21.1%) and caries in children (28.7% vs. 7.7%). Less than half of Malaysian and Australian nursing students reported that they received adequate OH training (48.4% vs. 36.6%, p ā¤ 0.01), especially in detecting oral cancer (18.0.0% vs. 22.6%, p ā¤ 0.01) and preventing oral diseases (46.7% vs. 41.7%, p ā¤ 0.01). Students in both countries demonstrated positive attitudes and believed in their role in OH care. Most students agreed that they should receive training in OH, especially in smoking cessation and providing OH care for patients with special needs. They also opined that a standardized evidence-based oral hygiene protocol is needed. CONCLUSION: Support for education and practice in this area of patient care suggested positive implications for further development of nurses' roles in OH promotion and management.
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ItemNo Preview AvailableCollaborative Oral Health Care(UBIQUITY PRESS LTD, 2021)
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ItemNo Preview AvailableOral health implications in patients with head and neck cancer(Elsevier BV, 2021-09)
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ItemNo Preview AvailableTen millennia of hepatitis B virus evolution(AMER ASSOC ADVANCEMENT SCIENCE, 2021-10-08)Hepatitis B virus (HBV) has been infecting humans for millennia and remains a global health problem, but its past diversity and dispersal routes are largely unknown. We generated HBV genomic data from 137 Eurasians and Native Americans dated between ~10,500 and ~400 years ago. We date the most recent common ancestor of all HBV lineages to between ~20,000 and 12,000 years ago, with the virus present in European and South American hunter-gatherers during the early Holocene. After the European Neolithic transition, Mesolithic HBV strains were replaced by a lineage likely disseminated by early farmers that prevailed throughout western Eurasia for ~4000 years, declining around the end of the 2nd millennium BCE. The only remnant of this prehistoric HBV diversity is the rare genotype G, which appears to have reemerged during the HIV pandemic.
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ItemNo Preview AvailableUtilising surface-level data to explore surface, tooth, individual and family influence on the aetiology of hypomineralised second primary molars(ELSEVIER SCI LTD, 2021-10)OBJECTIVES: Hypomineralised second primary molars (HSPM) are common developmental enamel defects. The aims of this study were to use surface-level data to explore the clustering of HSPM at four levels (family, child, tooth, surface). METHODS: This study of 172 twin pairs was nested within the Peri/postnatal Epigenetic Twin Study. HSPM was measured by standardised oral examinations at age 6 years. Multilevel logistic regression models were fitted to assess the correlation structure of surface level data and variation in HSPM. The associations between surface level risk factors and HSPM were then explored using the multilevel logistic regression model using the best fitting correlation structure. RESULTS: The prevalence of HSPM was 68 (19.8%) children, with a total of 141 (10.3%) teeth and 264 tooth surfaces (6.3%) affected. Multilevel models revealed that a hierarchical structure accounting for correlation at the family, child and tooth level best accounted for the variation in HSPM. The estimated variances from the best fitting model (Model 3) were largest at the family level (12.27, 95% CI 6.68, 22.51) compared with 5.23 at the child level and 1.93 at the tooth level. Application of regression analysis utilising this three-level correlation structure identified tooth/surface level factors in addition to the previously identified familial and individual risk factors for HSPM. CONCLUSION: In addition to familial (environmental and genetic) and unique child-level factors, the aetiology of HSPM is likely to be influenced by local tooth-level factors.
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ItemNo Preview AvailableStreptococcus salivarius K12 inhibits Candida albicans aggregation, biofilm formation and dimorphism(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 (pā<ā0.05). 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.