microbiology part 2 Flashcards
compare current hypothesis relating plaque to caries understand rationale against preventative strategies
what is kochs posulates
Koch’s postulates (/ˈkɔːx/) are four criteria designed to establish a causative relationship between a microbe and a disease.
is dental caries or gingivitis transferred between person to person
YES
is the pathogen present in health in dental caries or ginigitivitis
yes/often
does the pathogen satisfy kochs posulates in caries or gingivitis
no
does pathogen produces virulence factors in caries and gingivitis
no
how are conventional diseases transmitted
Sneezing, coughing through air and water droplets
do conventional disease meet kochs posulates
yes
what is dental disease described as
dysbiosis of the resident oral microbiota
where to the cariogenic bacteria in the biofilm come from
two hypothesis
- transmission eg from mother to baby
- the harmful pathogens are present even in health but in such low numbers that its not clinically relevant
how does dysbiosis occur
there must be some major ecological pressure - alters competitiveness
what are the major ecological changes that that place for caries to occur
regular sugar attacks
reduced saliva
acidic pH
when might people have reduced saliva flow
elderly people due to medication
or head and neck radiotherapy
what are the key features of cariogenic bacteria
acid producing
tolerating acid
what are some examples of cariogenic bacteria
MS
lactobacilli
bifidobacterium
scardovia
what are the three plaque hypothesis
specific
non specific
ecological plaque hypothesis
what is the specific plaque hypothesis
only one or two bacteria contribute to caries
describe non specific hypothesis
many species have a role in caries production
what is the ecological plaque hypothesis
that disease can be inhibited or prevented by controlling the ecological factors which can influence the shift of species growth in the oral microbiota( dysbiosis)
we can also promote symbiosis
what is specificity in disease found in
microbial function
describe the ecological plaque hypothesis
many species can contribute
caries is preventable by
direct inhibition of causative organisms
maintenance of natural balance
interfering the ecological shifts to stop the shift in bacteria
what shifts are involved with causing caries
increased sugar frequency —> more acid attacks
there more time at low pH
shift in the bacterial load
therefore health shifts to caries
what are the forms of sucrose that are found in the
sticky slime( extracellular polysaccharides) food reserves made from XS sugar( intracellular polysaccharides) fermentation process-lactic acid or other acids which acidifies the pH
what are the bacteria associated with gum disease - in the mixed culture
F nucleatum
P gingivalis
P nigrescens
what bacteria are associated with health - in the mixed culture
S gordonii S oralis A naeslundii N subflava V dispar
what bacteria are associated with disease - in the mixed culture
S mutans
L caesi
what could we alter when carrying out the experiment
the sugar content
and the pH
describe the experiment which models the oral biota
beneficial bacteria growing on agar plate
pH of 7
strep mutans
L caesi were both only at 1% in the population and non competitive
what were the results when glucose was pulsed in and pH was constant
nothing happened as the beneficial bacteria are growing and are more competitive than the disease bacteria
what were the results when glucose was pulsed in and pH was not constant
low pH
healthy species was reduced and the cariogenic bacteria increased to more than 50%
what is the relationship between pH and % of cariogenic bacteria
inverse relationship
what happens the lower the pH of the mouth
the more competitive the bacteria and greater % of cariogenic bacteria
what happens when fluoride is added
it slows down the acid production
what was the % of strep mutans when fluoride wasn’t present in the study
23%
what was the % of strep mutans when fluoride was present in the study
less than 3%
what was the pH in the study when fluoride wasnt present
4.55
what was the pH in the study when fluoride was present
5.55
what are the approaches for controlling dental caries
plaque control-brushing floss fluoride sugar substitutes antimicrobial and anti plaque modify the microbiota vaccination passive immunisation
what does fluoride do
it can enter the cell and inhibit glycolysis
stops the pH falling that much so disease causing bacteria cannot grow
give examples of sugar substitutes
bulking agents- sorbitol and xylitol
intense sweeteners - saccharin and aspartame
how do we control dental caries
bulking agents intense sweeteners weakly metabolised in acid stimulate saliva flow weak antimicrobial activity
what is the gold standard of antimicrobial, anti MS, anti plaque mouthwash
chlorhexidine- only used for a short period eg 7 days
in the mouth for 1-2 mins
why is triclosan phased out
found in the environment eg in polar bear cells
what is the pathway of fluroide ions
forms HF and shoots across the extracellular membrane. once enters the cell splits into H and F and the fluoride inhibits glycolysis enzyme pathway
what does streptococcus dentisani do
arginolytic
what does streptococcus A12 do
bacteriocin inhibits MS
how do we modify the microbiota
replacement therapy
genetically modified strep mutans introduced to kids and removed the enzyme that leads to lactic acid production and inhibits natural strep mutans
what are prebiotics
molecules that stimulate the growth of beneficial bacteria eg arginine in toothpaste
what is the full immune response found in the mouth
SIgA, IgG,neutrophils and complement
what are vaccines based on
whole cell
glucosyltransferases
cell wall associated proteins
examples of passive immunity
coat surfaces with antibodies or synthetic body fragments
advantage of passive immunity
safe acceptable
non invasive
no cross reaction with human tissues
no side effects
