Caries microbiology Flashcards
What is the pathogenesis of infection
• When microbes find a new host and start to multiply its called colonisation
• A balance can develop between colonised microbes and humans which is the normal flora
• If microbes cause disease it is an infection, caries is an infection
• If the source of microbe is a patient’s own flora it is called an endogenous infection
If the source of the microbe is flora from outside the patient’s own flora - called an exogenous infection
What is dental plaque
• A diverse microbial community (predominantly bacteria) found on the tooth surface, embedded in a matrix of polymers of bacteria and salivary origin
Plaque is the main aetiological agent associated with caries
Describe the oral microbiome
- At least 700 bacterial species
- Predominantly on hard tissues
- Also found on the dorsum of the tongue and on soft tissues (shedding)
- We are sterile at birth and we acquire bugs through food, milk, water, mother’s saliva etc
Outline plaque formation
- Pellicle formation
- Colonisation by pioneer bacteria (streptococcus species)
- Outgrowth
- Secondary colonisation by other organisms
- Climax community
What are the basic concepts of oral microbiology
- A wide variety of microbes regularly enter the oral cavity
- Host factors effect their growth and prevent many species from surviving
- Brushing and flossing clears some built up biofilm
- Oral antibiotics inhibit growth
- Symbiosis of the oral microbes that are able to survive these conditions form an elaborate scaffold that lives on the tooth enamel and at the interface with the gums
- It forms a barrier for incoming bacteria
What are the host factors
○ Saliva
○ pH
○ Temperature
Immune system
What is caries
• Loss of mineralized surfaces of the tooth
• Surfaces are permanently damaged
• Underlying dentine is at risk or damaged
• Multi-factorial disease
○ Microbial biofilms
○ Acidity, sugar metabolism
What makes someone low risk
○ Alkaline producing bacteria such as S. sanguinis
○ Unstimulated saliva flow >1ml/min
○ Infrequent sucrose consumption
Fluoride intake to levels allowing production of fluorapatite
What makes someone high risk
○ Acid producing bacteria such as mutans streptococci and lactobacilli
○ Unstimulated saliva flow of <0.7ml/min
○ Frequent consumption of high levels of sucrose and other fermentable carbohydrates
○ Little or no fluoride intake
Outline caries progression
- Adhesion
- Survival & growth
- Biofilm formation
- Complex plaque which is difficult to remove
- Acid
Caries and possibly irreversible damage
What are the key cariogenic pathogens
○ Streptococcus mutans ○ Lactobacillus acidophilus ○ Actinomyces viscosus ○ Candida albicans Nocardia spp.
What are the virulence factors of a prokaryotic cell
○ Pili for attachment
○ Capsule which is sticky and protects host immunity
○ Flagellum - swim through bacteria
Endotoxins - released from gram cell walls
Describe caries association with s. mutans
- Produces water soluble and insoluble extracellular polysaccharides from sucrose which help in colonization of the tooth surfaces by consolidating microbial attachment
- Ability to initiate and maintain microbial growth and to continue acid production in sites with a low pH
- Rapid metabolism of sugars to lactic and other organic acids
Can attain the critical pH for enamel demineralisation more rapidly than other common plaque bacteria
What is koch’s postulate
- The microbe must be present in every case of the disease
- The microbe must be isolated from the diseased host and grown in pure culture
- The disease must be reproduced when a pure culture is introduced into a susceptible host
- The microbe must be recovered from an experimentally infected host
Describe s. mutans
- Gram-positive coccus
- 8 serotypes
- Adhesion and biofilm formation
- Metabolizes dietary sucrose to form insoluble polymers of glucose – stick to surfaces
Survive in low pH environments – enamel dissolution
What are gluons
- S mutans can produce glucans which help in it’s adhesion
The more it adheres, the more colonisation and the more acid
What are the virulence factors
adhesins binding proteins sugar modifying enzymes polysaccharides acid tolerance and adaption
What are adhesions
○ Make up fibrillar layer of cell wall
Help to attach to teeth
What are sugar modifying enzymes
Take sugars to make glucans
What are polysaccharides
○ Protection from external environmental forces but also storage (glycogen)
What is acid tolerance and adaption
○ Has membrane pumps (ATPase) within the cell membrane that fire out hydrogen ions
○ As the pH goes down, we can put them straight back out and maintain internal equilibrium at a more neutral pH so it can survive in high acid conditions
Describe sucrose metabolism
- If you feed them sugar, they have enzymes that can produce glucans and fructans and these are very sticky
Glycolysis will take these sugars, produce carbon dioxide and that is the driving part in acid production
What are the types of glucans
water soluble
water insoluble
Describe water soluble glucans
○ Readily degraded for energy source
Formation of lactic acid
