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microbiology part 1 Flashcards

to review the microbial aetiology of caries and provide context for preventative approach objectives: revisit properties of dental biofilm review the methods to characterise the oral microbiome assess the evidence for the role of micro-organisms in caries describe the main causative bacteria define the properties of cariogenic bacteria

1
Q

what are dental biofilms

A

they are natural and beneficial

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2
Q

how many species are present in the dental biofilm

A

700+ species

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3
Q

what is the biofilm composed of

A

bacteria
viruses
fungi

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4
Q

what does the biome help with

A

with key functions
helps to regulate the immune system
and helps with host defences

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5
Q

what is desquamination

A

the shedding of epithelial cells- reduces the bacterial load

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6
Q

examples of non shedding surfaces

A

teeth
dentures
implants

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7
Q

what is the bacterial load like on non shedding surfaces

A

it is high unless you remove the load by eg brushing

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8
Q

how can we tell which bacteria are beneficial or harmful

A

by traditional culture such as

grow the organism

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9
Q

what are the issues with traditional culture

A

laborious
expensive
only half the species in the mouth grow on blood agar
very time consuming- need to do multiple tests and isolate the species

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10
Q

what are the issues with microscopy

A

only will tell you the shape of the species( cell morphology)

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11
Q

what does FISH stand for

A

fluorescent in situ hybridisation- can help recognise a few species

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12
Q

what are the molecular approaches to identify the species in the microbiome

A

HOMIM (human oral microbiome identification microarray )
DNA-DNA hybridisation
PCR
high throughput whole genome sequencing

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13
Q

what is the gold standard to see what species an organism is

A

high throughput whole genome sequencing- and put into the database and you can see which organism is present

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14
Q

what is metagenomics

A

complex clinical sample such as plaque
extract DNA
cut DNA
sequence and then the short fragments will make a long sequence
tested across a database and we can see which species are present

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15
Q

what does metatranscriptonomics look at

A

RNA to see which proteins are transcribed

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16
Q

what is HOMD

A

human oral microbiome database

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17
Q

how is the bacteria in the dental biofilm organised

A

structurally organised

functionally organised

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18
Q

why are bacteria in the biofilm functionally organised

A

so that the aerobic organisms are nearer the surface for O2

and anaerobic at the base

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19
Q

what are the features of the dental biofilms

A 
concerted and collaborative metabolism 
food chains
environment modification
matrix formation
cell-cell signalling
complex interactions- balance
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20
Q

why are dental biofilms helpful

A

they help get rid of harmful organisms in the mouth due to pathogen exclusion

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21
Q

how can the load of helpful bacteria in the dental biofilm be reduced

A

due to long term antibiotic therapy

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22
Q

what can be the result of long term antibiotic therapy

A

overgrowth of yeasts

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23
Q

bacteria from which organ can cause a inflammatory reaction

A

gut and the mouth but rare

eg Crohns disease in the gut

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24
Q

why do we rarely see inflammatory reaction in the mouth

A

because the bacteria communicate between one another and the host

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25
what is the entero salivary nitrate circulating system
where nitrate from green vegetables is reabsorbed from the gut and appears in saliva and the beneficial bacteria can break it down to nitrite which modifies blood pressure . and nitrite that is swallowed becomes acidified nitric oxide which is antibacterial and stimulates mucus
26
where does the body get nitrate from
from green veggies we eat
27
what does the nitrate get converted to
get converted into nitrite by beneficial bacteria in the oral cavity
28
why is nitrite good
it can reduce blood pressure
29
what does XS nitrite that is swallowed get converted into
acidified nitric oxide
30
where is the XS nitrite converted
in the stomach
31
why is acidified nitric oxide good
due to the fact it stimulates mucus production which protects the stomach lining and it is antibacterial
32
examples of bacteria seen in carious lesions
strep mutans lactobacillus other acidogenic/tolerating bacteria
33
which bacteria are seen in health
``` strep oralis/mitis fusobacterium nucleatum actinomycetes spp haemophillus spp neisseria spp ```
34
why is caries multifactorial
as it has many components such as: susceptible host environmental factor key oral organisms
35
what factors are included in environmental factors
cariogenic diet poor oral hygiene low saliva flow rate
36
what happens to older peoples flow rate of saliva
decreases- side effect if medication eg blood pressure medication
37
what factors are including in confounding factors
fluoride availability diverse natural microbiota non specific virulence traits
38
what is the evidence that microbes are involved in the aetiology of dental caries
gnotobiotic( known life) animal studies:artificial conditions where they are not exposed to organisms and then micro-organisms are introduced and we see the effect
39
gnotobiotic animal studies showed
specificity of certain microrganisms- eg lactobacilli causes caries diet- we do not have caries if fermentable sugars are not present transmission- from infected animal to non infected antim antimicrobial agents- effective antimicrobials prevent caries
40
why ca we not do germ free ethical studies on humans
due to ethical reasons
41
what is a cross sectional study
where we take a group of people- at one time point | sample of plaque and analyse for which species and see where caries is or isn't
42
what is the issue with cross sectional studies
cheap but only show associations- do not know certainly if the bacteria found in the lesion caused the lesion or grew as a consequence of the lesion
43
what is a longitudinal studies
small group of people- caries free choose caries prone site a % of those people should develop caries in that area in a few years monitor every 3-6 months for several years compare the microorganisms before during and after
44
what are the disadvantages of longitudinal studies
expensive | takes a lot of time- not many done
45
Vaccination
Vaccination against strep mutans in rodents and primates
46
Why are vaccinations for varies not introduced to humans
There were a few side effects and the public confidence in vaccines was little so the cost of clinical trials But fluoride was having an effect Vaccine hasn’t been tested in human clinical trials
47
what serotype is found of strep mutans
c e f
48
what serotype is found of strep srobinus
d | g
49
what species of actinomyces is present
a naeslundii a odontolyticus a isrealii
50
what species of bifidobacteria
bifidobacterium
51
which species of candida is found
c albicans
52
describe strep mutans
gram +ve cocci found on hard surfaces- non shedding surfaces implicated in initiation of caries
53
describe lactobacillus
gram +ve rods | implicated in advanced dental caries
54
describe bifidobacterium ( more recent years)
gram +ve rods branched cells recently implicated caries
55
what are the difficulties with trying to associate microorganisms with dental caries
disease occurs at sights where there is natural biome difficult to correlate microbiota to enamel status lesions can remineralise pathogenic traits are relatively non specific multifactorial nature of caries
56
what bacteria is found at caries sites
strep mutans but not always | in both proportions and isolation frequencies
57
which bacterias have an inverse relationship
between strep mutans and strep sanguinis
58
what % of caries had more than 10% MS
71%
59
what percentage of caries free fissures had no detectable MS
70%
60
when does MS first start to show
early demineralisation
61
can caries also occur if MS is not present
YES
62
examples of acidogenic bacteria
strep mitis | strep oralis
63
give examples of lactate utilising bacteria
veillonella
64
what is lactate converted to
propionate or acetate
65
describe veillonella
gram negative coccus anaerobic utilises lactic acid in plaque
66
name base generating species
s salivarius will make the pH basic when urea is present s sanguinis will make the pH basic when arginine is present a naeslundii will make the pH basic when urea is present
67
when will s salivarius make the ph basic
when urea is available
68
when will s sanguinis make the ph basic
when arginine is present
69
when a naeslundii will make the ph basic
when urea is available
70
which species is found in people with low caries or no caries
strep dentisani | strep A12
71
what do both strep dentisani and strep A12 do
they are arginolytic meaning they break down arginine into ammonia snd inhibits strep mutans
72
what can strep dentisani and strep A12 be used as
As probiotic
73
describe the urea to ammonia conversion
urea + h20-----> ammonia + CO2 by the enzyme urease
74
describe the arginine deiminase system
arginine---->citulline+ ammonia----> ornithine + carbamyl- P----> ATP+ C02 + ammonia
75
what bacteria is associated with childhood caries/nursing bottle caries
mutans streptococci | lactobacilli
76
which bacteria is associated with root surface caries in early studies
actinomyces spp
77
which bacteria is associated with root surface caries in later studies
MS | lactobacilli
78
which bacteria is associated with root surface caries in recent studies
diverse microbiota actinomyces spp- A israelii and A gerensceriae MS gram negative rods
79
what bacteria do you find in infected dentine
MS lactobacilli actinomyces spp- A israelii and A gerensceriae gram negative anaerobic rods - prevotella
80
what molecular changes do you find in infected dentine
strep mutans eubacterium saburreum diverse array of lactobacillius diverse array of prevotella
81
what else is found in infected dentine
acidogenic bacteria | combined with proteolytic and collagenolytic bacteria
82
characteristic of cariogenic bacteria
rapid sugar transport and acid production PEP-PTS aciduricity EPS IPS

CSA (51 decks)

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