Microbiology of caries Flashcards
What are biofilms made up of?
Diverse composition of 700+ species with bacteria, fungi and viruses etc, the composition is relatively stable.
What type of surfaces permit heavy biofilm formation?
Non shedding (teeth, dentures and implants)
What does desquamation help do?
Reduces microbial load on mucosal surfaces
What are the cons of traditional culture?
Laborious, expensive and only 50-70% of microbiota can be cultured. Then multiple tests have to be done to work out what each organism is.
What is the con of light and electron microscopy?
Only cell morphology
What is fluorescent in situ hybridisation?
A probe can be labelled with a fluorescent dye and will bind (hybridise), on the basis of complementary base pairing to the matching DNA in the cells (in situ).
What are the molecular approaches (culture dependent)?
- PCR
- DNA-DNA hybridisation (checkerboard)
- Human microbiome identification microarray - gold standard
- Whole genome sequencing (metagenomics)
What are the databases for oral microbiomes?
Human microbiome consortium
Human oral microbiome database
In health, how is a dental biofilm organised?
Structurally and functionally with anaerobes at the bottom and aerobes at the top/outside with organisms that feed off lactic acid under the tooth surface.
What are features of a multispecies biofilm?
Concerted and collaborative metabolism Food chains Environment modification Matrix formation Cell-cell signalling Complex interactions = balance
What is colonisation resistance?
Colonisation resistance is the term used to describe the microbiota’s capacity to limit the introduction of exogenous microorganisms and pathobiont expansion.
What is cross talk immunomodulation?
Down regulation of potentially damaging pro inflammatory host responses
Stimulation of beneficial host responses
Promoting host-microbe balance (symbiosis)
What is the entero-salivary nitrate circulatory system?
Where dietary nitrate goes from nitrite to acidified nitric oxide which decreases blood pressure and increases gastric mucus which has an antibacterial effect.
What organisms are involved in dental health?
Strep mitis/oralis Actinomyces spp Haemophilus spp Nieseria spp Fusobacterium spp
What organisms are involved in caries?
Acid tolerating bacteria:
Mutans streptococci
Lactobacilli
Bifidobacterium
What are the drivers of change (what causes caries)?
Key oral micro-organisms, susceptible host (uncleaned tooth surface) and environmental factors (frequent fermentable carbohydrates, poor oral hygiene, low salivary flow rate)
What are confounding factors in the development of caries?
Fluoride availability, diverse natural microbiota and non specific virulence traits.
What are gnotobiotic animal studies?
Animals not exposed to micro-organisms the micro-organism is introduced to see the effect without confounding factors.
What are cross sectional human epidemiology studies?
A cross-sectional study involves looking at data from a population at one specific point in time. They only show association not causation (bacteria could increase as a consequence of caries) however they are cheap.
What are longitudinal studies?
Subjects are followed over time with continuous or repeated monitoring of risk factors or health outcomes, or both. They do show cause and effect but are expensive.
What are mutans streptococci?
Gram positive cocci/rods/cocco-bacilli
Found on non shedding surfaces
Implicated in initiation of caries
What are lactobacilli?
Gram positive rod found in advanced dental caries
What are bifidobacteria?
Gram positive rod with branched cells implicated recently in caries
What are the challenges in sampling bacteria for caries studies?
Disease occurs at sites with natural diverse microbiota and pathogens found at healthy sites as minor components of biofilm.
Difficult then to correlate microbiota to enamel status
Lesions can remineralise and compromise studies
Multifactorial causes of caries
What is the relationship found in cross sectional culture studies in regards to strep mutans?
Increased MS at caries sites
Inverse relationship - MS and sanguinis
Some sites with caries have no MS
Not diagnostic as some caries free fissures has MS