Caries Flashcards
quorum sensed by
autoinducers
quorum and biofilms
activate genes that support survival or are beneficial in community/biofilm
EPS secretion, metabolic changes, drug-resistance genes
different between Gram= and Gram-
coordination of population
quorum sensing in Gr. negative bacteria
low cell density: low AHL concentration, no gene expression
high cell density: high AHL concentration, transcription activated
function of polysaccharides
structure
buffer for pH
binds to nutrients - concentrate near bacteria
retain water
prevent or impede phagocytosis
bind to antibiotics
promotes lateral gene transfer
increase antibiotic resistance
how do polysaccharides increase antibiotic resistance
pH changes
decrease in active growth
physical separation of compound from bacteria
other bacteria available to die first
acquiring antibiotic resistance genes
vertically and horizontally
transformation, transduction, conjugation
core genomes of bacteria acquire mutations over time which can limit susceptibility to
antibiotics
biofilms limit what and promote what
limit penetrations of antibiotics and promote the spread of antibiotic resistance genes
furanones
inhibit bacterial colonization and biofilm development
inhibit normal signaling through AHL quorum-sensing
dental caries
a multifactorial, biofilm-associated disease characterized by dissolution of tooth hard tissue due to the attack of acids produced by bacteria in dental plaque
dental caries etiology
host factors: saliva, immune status, tooth strength
diet: fermentable carbohydrates
plaque microorganisms: cariogenic bacteria - S. Mutans
time: both longitudinal and frequency of eating and cleaning
cariogenicity
the ability to initiate tooth decay or caries
cariogenic pathogens have these features
involved biofilm formation (biofilm former)
compete for resources and ecological niches (competitive)
produce acids from carbohydrates (acidogenicity)
survive and continue to produce acids at low pH (aciduricity)
streptococcus mutans
Gram +, cocci in chain, most important
lactobacillus
gram +, rods, grow well at pH 5, progression, deep lesions
actinomyces
gram +, branching filament, root caries
characteristics of S. Mutans
initiates biofilm formation
generates lots of EPS
highly competitive
effective and rapid use of many sugars
grow at low pH
_____ allows S. mutans to outcompete other bacteria
sucrose
S. mutans - sucrose-dependent biofilm formation
glucan and fructan are examples of EPS
-form part of the plaque matrix
-facilitate S. mutans adherence to surface
-serve as carbohydrate storage/reserve
-as targets for other bacteria to bind to
Adhesin Ag I/II protein and receptor Gp-340
functions of glucan and fructan
provides receptors for other bacteria
can act as a carbon source
fermentation
a pathway in which the reducing power generated by oxidative reactions is re-oxidized by metabolites produced by the pathway
organic acids
bacteria produce organic acids from fermentable carbohydrates
heterofermentative bacteria
produce acetic, propionic, succinic, formic
homofermentative
produces S. mutans > 90% lactic acid
pKa of lactic acid
3.85
S. mutans ferments sucrose to
lactic acid
the stephan curve
describes the effect of fermentable sugars in ingested foods on plaque pH
demineralisation of enamel and dentin occurs when pH
enamel: < or = 5.5
dentin: < or = 6.2
S. mutans intracellular polysaccharide
storage form of carbohydrate, produced during excess sucrose
IPS serves as a source for energy and acid production, contributes to acidogenicity
how does IPS contribute to aciduricity
IPS provides energy for ATPase
ATPase drives protons out of cells
helps maintain neutral pH in the cytoplasm
inhibiting S. mutans
fluoride treatment
inhibiting enolase
antibiotics
fluoride treatment
forms fluorapatite instead of hydroxyapatite during remineralisation
less soluble than regular hydroxyapatite
converts 2-PG to PEP
inhibits glucose utilization and lactic acid production
antibiotic treatment in inhibiting S. mutans
systemic antibiotics - Penicillin
topical - chlorhexidine rinse - prevents plaque formation
