Mutans streptococci Flashcards
What are the 2 common mutans streptococci in humans
St. mutans (70-80%)
St.sobrinus (20-25%)
Name 4 virulence factors of Streptococci mutans that makes them cariogenic
1.Produce extracellular polysaccharides-glucan /fructan (sucrose dependent )
2.Great Carbohydrate fermentors ->lots lactic acid
3.Aciduric-survive low pH
4.Store polysaccharides intracellular so can use when low exogenous carbohydrates
How does producing extracellular polysaccharides help St. mutans become more virulent
Uses Glucose transferase to convert sucrose to glucan
Glucan branches and becomes more insoluble and adheres firmly to tooth surface - allows no diffusion in/out of formed plaque so Calcium blocked entry into the tooth so no enamel remineralisation and tooth gets no nutrients ( go to the St.mutans)
Also makes fructan - stores carbohydrates so prolongs lactic acid production and low PH longer
How does St mutans being a carbohydrate fermenter help its virulence in caries
Can ferment all simple sugars except mannitol/sorbitolso produces lots lactic acid -(pH3.13 ) that demineralises tooth
How does acidic nature help St mutans
As it ferments and causes acidic environments it allows it to survive in the lower pH as fermentation occurs ( pH 5.5 )
How does St mutans being able to store intracellular polysaccharides help its virulence in caries
when no exogenous carbohydrate sources it can use its stired glycogen to facilitate ongoing fermentation and the acid environment
What type bacteria is Streptococci mutans
Gram +ve cocci -facultative anaerobe( grows in anerobic and aerobic conditions )
What type of organism is lactobacilli
Gram +ve rod bacterium -microaerophilic (like low O2 levels)
NAme 2 properties of lactobacilli that make it cary forming
Acidic (metabolism at pH,4)
carbohydrate fermenter - makes lactic acid
what type of caries is lactobacilli found in
Severe advanced caries ( not initial cavities ( that’s St.mutans )
