A proteomic investigation of Fusobacterium nucleatum alkaline-induced biofilms.

BACKGROUND: The Gram negative anaerobe Fusobacterium nucleatum has been implicated in the aetiology of periodontal diseases. Although frequently isolated from healthy dental plaque, its numbers and proportion increase in plaque associated with disease. One of the significant physico-chemical changes in the diseased gingival sulcus is increased environmental pH. When grown under controlled conditions in our laboratory, F. nucleatum subspecies polymorphum formed mono-culture biofilms when cultured at pH 8.2. Biofilm formation is a survival strategy for bacteria, often associated with altered physiology and increased virulence. A proteomic approach was used to understand the phenotypic changes in F. nucleatum cells associated with alkaline induced biofilms. The proteomic based identification of significantly altered proteins was verified where possible using additional methods including quantitative real-time PCR (qRT-PCR), enzyme assay, acidic end-product analysis, intracellular polyglucose assay and Western blotting. RESULTS: Of 421 proteins detected on two-dimensional electrophoresis gels, spot densities of 54 proteins varied significantly (p < 0.05) in F. nucleatum cultured at pH 8.2 compared to growth at pH 7.4. Proteins that were differentially produced in biofilm cells were associated with the functional classes; metabolic enzymes, transport, stress response and hypothetical proteins. Our results suggest that biofilm cells were more metabolically efficient than planktonic cells as changes to amino acid and glucose metabolism generated additional energy needed for survival in a sub-optimal environment. The intracellular concentration of stress response proteins including heat shock protein GroEL and recombinational protein RecA increased markedly in the alkaline environment. A significant finding was the increased abundance of an adhesin, Fusobacterial outer membrane protein A (FomA). This surface protein is known for its capacity to bind to a vast number of bacterial species and human epithelial cells and its increased abundance was associated with biofilm formation. CONCLUSION: This investigation identified a number of proteins that were significantly altered by F. nucleatum in response to alkaline conditions similar to those reported in diseased periodontal pockets. The results provide insight into the adaptive mechanisms used by F. nucleatum biofilms in response to pH increase in the host environment.

Caries experience in existing and new nursing home residents in Adelaide, Australia.

OBJECTIVES: The Adelaide Dental Study of Nursing Homes was instigated to provide comprehensive information concerning oral disease experience, incidence and increments in a random sample of those older South Australians residing in Adelaide nursing homes. METHODS: This paper presents caries experience results for existing and new nursing home residents, and caries incidence and increments for existing residents, from dental inspections conducted at the baseline and one-year data collections. RESULTS: The residents in this study were very functionally dependent, medically compromised, cognitively impaired and behaviourally difficult older adults, the great majority of whom had moderate to severe cognitive impairment. Residents gave their carers many complex and challenging behavioural problems during oral hygiene care provision. Existing and new residents had similar dental history, oral hygiene, and sociodemographic characteristics, and similar cognitive, medical, functional, and nutritional status. Oral disease experience was high in both existing and new residents. There were no significant differences between existing and new residents for their dentate status, tooth status, coronal caries experience, or root caries experience, with the exceptions that new residents had significantly greater mean number of teeth, more filled coronal and root surfaces, and also new residents had significantly fewer decayed retained roots. Large numbers of tooth surfaces were covered in plaque and debris that negated more precise assessment of caries. The existing residents had caries increments on both coronal (2.5 surfaces) and root surfaces (1.0 surfaces) over the one-year period. Coronal caries incidence was 64% and root caries incidence was 49% of existing residents. CONCLUSIONS: Oral disease experience was high in both existing and new residents. There were few significant differences between existing and new residents' oral health status. New residents were being admitted to nursing homes with a compromised oral health status. Coronal and root caries increments and incidence were high for existing residents over the one-year period.