Microbiology of caries I Flashcards
Revisit the properties of dental biofilms Review the methods to characterise the oral microbiome Assess the evidence for the role of microbes in caries Describe the main causative bacteria Define the properties of cariogenic bacteria
Give 5 properties of dental biofilms
- Diverse composition (700 +species)
- Bacteria, fungi and viruses
- relatively stable composition over time
- Desquamation reduces microbial load on mucosal surfaces
- ‘Non shedding surfaces’ (denture, teeth,implants)
permit heavy biofilm formation unless its controlled
How do we distinguish between beneficial and pathogenic microorgansmism?
- Traditional culture
-Laborious:expensive: only 50-70% of oral mciorbiota can be cultured
- multiple tests to identify and anime the isolates
- tedious
- different conditions required by different microbiota - Microscopy
- Conventional (light and electron microscopy)
- FISH (fluorescent in situ hybridisation) - Molecular (cult-independent)
- PCR
- DNA-DNA hybridisation
- Human oral microbiome identification microarray (HOMIM) larger number of pre selected species that can be detected
- High thoroughput whole genome sequencing (metagenomics/metatransciptomics)
What 3 characteristics are found in dental biofilms
-Structurally organised
-Functionally organised
-Undergo constant organisation
What are the 6 features of multi-species biofilms
- concerted and collaborative metabolism
- food chains
- environment modification
- matrix formation
- cell - cell signalling
- complex interactions= balance
what does symbiosis mean
oral biofilms are natural and beneficial
what does colonisation resistance involve
-long term antibiotic therapy- overgrowth by yeasts
-excludes exogenous microbes
what is immunomodulation
regulation and modulation of immunity that might be achieved by reducing or enhancing immune response
- down regulation of potentialy damaging pro-inflammatory host reponse
- stimulation of beneficial host response
- promote host-microbe balance
- dietary nitrate - acidified nitric oxide (help decrease bp)
-Blood pressure decreases; gastric mucus increases; antibacterial increases
what are the environmental factors of caries
-cariogenic diete
- frequent femetable sugars
-poor oral hygiene
-low saliva flow rate
what are the confounding factors of caries?
fluoride availabilty
diverse natural mciobiata
non specific virulence traits
what are the 3 types of evidence found for the role of mricobes in aetiology of dental caries
Gnotobiotic
Human epidemiology
Vaccination
How does Gnotobiotic show the role of mricobes in aetiology of dental caries
- controlled environment where usually no microbes present (animal studies)
- specificity- some bacteria are more cariogenic than others
- diet- importance of fermentable sugars
- transmission - from animal to animal
-Antimicrobial agents- effective antimicrobials prevent caries
How does Human epidemiology studies show the evidence for role of microbes in aetiology of dental caries
- cross sectional - cheap but only show associations
- Longitudinal - show cause and effect relationships
How does Vaccination show the evidence for role of microbes in aetiology of dental caries?
rodents and primates- active vaccination can protect
Name 5 implicated microorganisms in caries
Mutans streptococci (MS) (gram+ cocci, found on hard non shedding surfaces, iniation of caries)
Lactobacillus- (gram+ rod advanced dental caries)
Bifidobacteria
Candida
Actinomyces