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IOE - microbiology > Plaque > Flashcards

Plaque Flashcards

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Biology 101 flashcards
1
Q

define plaque

A

natural, normal + beneficial to health

community of micro-organisms found on the tooth surface as a biofilm embedded in a matrix of polymers of salivary and bacterial origin

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2
Q

define microbial community

A

interactive mixture of organisms

many types of bacteria and other organisms are found in dental plaque BUT they don’t exist in isolation, they function as a community
(properties of the WHOLE is more than the sum of the PARTS)

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3
Q

what are biofilms

A

bacteria that exist on surfaces as in nature all microorganisms have to stick to a surface in order to survive and exist

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4
Q

where do biofilms exist and why

A

throughout nature

way microorganisms have adapted to survive

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5
Q

how is plaque beneficial to the host

A

contributes to host defences helping to keep out organsims that we come into contact with daily

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6
Q

where is plaque preferentially located and why

A

retentive and stagnant sites (suffer most dental disease)

these sites are protected from the oral environment, saliva flow, chewing + patients find the most difficult to clean

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7
Q

give 5 non dental sites biofilms exist on

A

large distribution water pipes
contact lenses (can cause conjunctivitis etc)
machinery in industry
hip replacement implants (if contaminated when being inserted)
legionella (organism causing legionnaires disease - ie from poorly maintained water systems in hospitals / hotels if not kept at high enough temp and Cl / other agents not added at right concentration)

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8
Q

give 4 issues with biofilms

A

1) novel microbial phenotype (ie properties)
2) altered pattern of gene expression
3) exopolymer synthesis up-regulated
4) incd tolerance to inhibitors + stresses (clinically relevant)

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9
Q

what does the issue of novel microbial phenotype (ie properties) mean

A

properties of an organism growing on a surface are different to when its growing in conventional liquid culture

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10
Q

why do organisms alter their gene expression when growing on a surface

A

recognise the significance of a surface

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11
Q

what are exopolymers and why is their synthesis upregulated

A

sticky polymers - help in the adhesion of bacteria

helps organisms bind to the surface and protects them from the hostile environment

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12
Q

what are the 7 stages of dental biofilm formation

A

1) conditioning film
2) transport of microbes
3) reversible phase
4) irreversible phase
5) secondary colonisation [co-adhesion]
6) growth & matrix synthesis
7) detachment

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13
Q

stage 1) outline what the conditioning film is

A

ACQUIRED PELLICLE

as soon as a surface appears in the mouth its covered with a film of proteins and glycoproteins in seconds (these are absorbed onto it)

this is what microbes attach to

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14
Q

stage 1) define acquired pellicle

A

name for conditioning film in the DENTAL context

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15
Q

stage 1) what can the conditioning film come from if a surface is near the gum

A

GCF

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16
Q

stage 1) what is GCF

A

fluid that flows around the gum and bathes the roots of the teeth around the gingival crevice

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17
Q

stage 2) how are microbes transported to the surface

A

passively by flow of saliva

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18
Q

stage 2) how else can microbes in some environments be motile

A

have organelles allowing this

generally in mouth = not motile

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19
Q

stage 3) what are the properties of interactions in the reversible phase

A

long range
v weak
non-specific

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20
Q

stage 3) what may the reversible phase occur instead of

A

being swept round in saliva

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21
Q

stage 3) what is the reversible phase and what is it due to

A

molecules in a fluid environment have an ionic group on them with +/- charge SO get an interaction between charged surfaces

due to electrical charge associated w the surface of a microorganism interacting w a charge on the proteins attached to the surface

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22
Q

stage 3) what happens if organisms are held in this loose reversible way for sufficient time

A

possibility for interaction to become more permanent

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23
Q

stage 4) what are the properties of interactions in the irreversible phase

A

short range
very strong
specific
more permanent than the reversible phase

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24
Q

stage 4) what do interactions in the irreversible phase involve

A

ADHESINS interacting with a RECEPTOR on the saliva coated surface

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25
Q

stage 4) what are adhesins and receptors

A

adhesins = specific molecules on the microbial cell surface

receptors = complimentary molecule

so its a VERY SPECIFIC binding

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26
Q

stage 4) how has such specific binding / strong attraction been enabled

A

millions of years of evolution

specific organisms evolve and adapt to interact w host molecules and host in a way these microorganisms = actually beneficial to us to have colonising the mouth

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27
Q

stage 5) what are the properties of secondary colonisation / co-adhesion

A

increased diversity
metabolic interactions
environmental modification

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28
Q

stage 5) what is secondary colonisation / co-adhesion

A

once early colonisers / pioneer species have attached it is possible for other organisms to come and attach to them (PURE ECOLOGY)

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29
Q

stage 5) how is potential for metabolic interaction optimised

A

these organsisms are in v close physical contact w each other

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30
Q

stage 5) how is the environment modified and what does this mean

A

organisms make it more suitable for their growth (ie consume O2 to make it more anaerobic)

means more fastidious organisms can colonise

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31
Q

stage 5) what is the process of 1 organism attaching to another already attached one called

A

CO-ADHESION

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32
Q

stage 5) what happens after attachment if the environment is suitable

A

organisms can start to grow and synthesise…

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33
Q

stage 6) what are extracellular polysaccharides (EPS)

A

the sticky polymers that these organisms can produce

the sticky polymers synthesised = called the biofilm MATRIX

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34
Q

stage 6) what happens as the biofilm starts to develop and mature

A

it gets more complex and more stable

there is more structure to it as the organisms are interacting w one another

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35
Q

stage 6) what can happen if the environment becomes unfavourable for organisms growth

A

organisms are not unaware of their environment so notice this and its possible for them to detach…

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36
Q

stage 7) what is detachment

A

enzymatic cleavage of adhesins which then colonise new sites more favourable for their growth

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37
Q

stage 7) how are adhesin receptor interactions cleaved (broken)

A

by enzymes produced by some bacteria

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38
Q

stage 1) what is the depth of the acquired pellice

A

up to 1um thick

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39
Q

stage 1) what is the acquired pellicle mainly derived from

A

saliva
GCF
microbes from the bacteria

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40
Q

stage 1) list 6 molecules in saliva that have been found in the pellicle

A

1) amylase
2) immunoglobulins
3) proline rich peptides (PRP)
4) mucins
5) statherin
6) agglutinins

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41
Q

stage 1) what is the normal function of amylase and its function in the pellicle

A

enzyme produced in saliva that breaks down starch

free in saliva

in pellicle = retains its activity and still functions

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42
Q

stage 1) list 2 molecules in bacteria that have been found in the pellicle

A

1) glucosyltransferases

2) glucans

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43
Q

stage 3) how can 2 -vely charged molecules form an interaction despite usually repelling

A

lots of cations present (Mg and Ca) in saliva

so the 2 -ves get BRIDGED by a cation

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44
Q

stage 4) what have scientists determined to be the adhesin and receptor for STREPTOCOCCUS SPP.

A

adhesin = antigen I/II

receptor = salivary agglutinin

45
Q

stage 4) what have scientists determined to be the adhesin and receptor for MUTANS STREPTOCOCCI

A

adhesin = glucan-binding protein

receptor = glucan

46
Q

stage 4) what have scientists determined to be the adhesin and receptor for ACTINOMYCES NAESLUNDII

A

adhesin = type 1 fimbriae

receptor = proline-rich proteins (PRP)

47
Q

stage 4) how could we use the knowledge of adhesins and receptors of different bacteria for clinically

A

make analogues of these molecules

flood a surface with molecules that will saturate all binding sites so organism cant attach

48
Q

stage 4) what do AGGLUTININS do

A

its interactions occur in solution in saliva NOT at the surface

they bind viruses and non oral bacteria so we swallow them

49
Q

stage 4) what do PROLINE RICH PEPTIDES (PRPs) do

A

designed to absorb to the surface and favourably allow certain molecules selectively to colonise

prps are prevalent in saliva

1) when in solution in saliva / solution = theyre curled up so bacteria cant bind
2) when lands on a surface = unwinds exposing receptors (cryptitopes) so bacteria CAN bind

50
Q

stage 4) what are cryptitopes

A

the hidden receptors for bacterial adhesins on PRP that are exposed when it unwinds

greek
cryptic = hidden
topo = place
hidden place

51
Q

which 4 species are common at the start of plaque formation

A

1) streptococcus mutans
2) streptococcus sanguinis
3) streptococcus oralis
4) streptococcus salivarius

52
Q

which type of organisms become more prevalent as the biofilm matures and why

A

aneorobic (ie fusobacterium nucleatum and black-pigmented anaerobes and facultative aerobes like actinomyces naeslundii)

pioneer species consume O2 when they grow

53
Q

what common secondary coloniser is a bridging organism, explain this property

A

fusobacterium nucleatum

it can CO-ADHERE to ALL of the early colonisers and on its surface it has molecules which enable many late colonisers to attach to it
SO bridges early and late colonisers

54
Q

why can we get a bad smell as plaque matures

A

complex biofilm with lots of anaerobic bacteria (which are implicated in perio disease) which make malodorous compounds causing the smell

55
Q

as biofilm develops this enables cell signalling interactions, explain these

A

cells produce diffusible molecules

gram +ves = produce peptides (if they receive many of these peptides they know = many similar organisms around + environment favourable)

gram -ves = produce autoinducer-2 (AI-2)

56
Q

as biofilm develops this enables metabolic interactions, explain these

A

its hard for the organisms to get their nutrients to grow (complex molecules to / multiple organisms have to interact to break them down

so we get a food chain (organism breaks down a molecule used by another organism and produces alternate products)

57
Q

give an example of sequential breakdown starting with glucose

A

1) glucose to lactic acid / lactate (by streptococcus)

2) lactic acid to acetate and propionate (by veillonella)

58
Q

why is the presence on veillonella good in the sequential breakdown of glucose

A

converts lactic acid into weaker acids so LESS caries as prevents demineralisation of enamel caused by lactate

59
Q

how long would bacteria from a single mouth be laid end to end

A

50km / 30 miles

60
Q

what do bacteria grow off of and live on

A

grow off molecules produced by the host

live on salivary molecules

61
Q

what do patients fed by stomach tube and not taking anything in in their diet STILL have

A

diverse set of microbes bc of the benefits

62
Q

what salivary molecules do bacteria often live on

A

MUCIN (glycoproteins)

proteins with carbohydrate side chain
these are complex + chain of different sugars hangs off them

63
Q

what is the process of breaking down mucins

A

no 1 organism has ALL the enzymes to do it

the terminal sugar must be removed before sugars next to them are exposed so can be removed

CONCERTED (bc of metabolic cooperation) + SEQUENTIAL BREAKDOWN

64
Q

what can be done to a mucin once all its sugars are removed

what is the result of this process (breaking down host glycoproteins)

A

organisms producing proteases break down the protein backbone into PEPTIDES then AMINO ACIDS

little effect on pH as its a complex, involved process

65
Q

what is the plaque matrix

and what % of plaque volume does it make up

A

sticky polymers from the host + bacteria making up signif vol of the biofilm

30%

66
Q

list 4 bacterial polysaccharides found in the plaque matrix

A

1) glucan
2) mutan
3) fructan
4) heteropolymers

67
Q

list a bacterial polymer found in the plaque matrix

A

e-DNA (extracellular DNA)

when some of the bacteria lyse, their dna stays there and acts as a part of the scaffold

68
Q

which 2 enzymes can break sucrose down

A

Glucosyltransferase (GTF)

Fructosyltransferase (FTF)

69
Q

sucrose -> glucan +___

which enzyme catalyses this

A

sucrose -> glucan + fructose

Glucosyltransferase (GTF)

70
Q

sucrose -> fructan + ___

which enzyme catalyses this

A

sucrose -> fructan + glucose

Fructosyltransferase (FTF)

71
Q

glucan is…

GTF sucrose breakdown

A

glucose residues from sucrose breakdown stuck together

72
Q

fructose molecules are… so…

GTF sucrose breakdown

A

sticky and insoluble so stay in the biofilm and bind it firmly to the tooth surface

73
Q

fructan is…

FTF sucrose breakdown

A

polymer of all the fructose molecules

labile + used by bacteria as a food reserve

74
Q

give 6 functions of the plaque matrix

A

1) protection
(from extreme environment and host defences)
2) nutritional reserve (glucans and fructans utilised)
3) stabilises biofilm (structural support)
4) bioactive
(interacts with other molecules so retains some enzymes, ions which are bound to the matrix)
5) water retention
(prevents dessication as bacteria dislike being dehydrated)
6) retards penetration of antimicrobial agents
(many antimicrobial agents have a charge so matrix can bind + prevent penetration of the agent into the biofilms depths )

75
Q

which 6 beneficial interactions occur in the microbial community that is the biofilm

A

1) food chain
2) enzyme complementation (sharing of enzymes)
3) cell-cell signalling (“QUORUN SENSING”)
4) inhibitor neutralisation
5) subversion of host defences to protect the organisms
6) gene transfer (may get antibiotic resistance gene passed around organisms)

76
Q

which 6 antagonistic interactions occur in the microbial community that is the biofilm

A

1) produce inhibitory molecules (ie bacteriocins, acids, H2O2) to give themselves an advantage so they try and inhibit competing organisms
2) bacteriocins (peptide, can inhibit closely related organisms)
3) hydrogen peroxide (whitens teeth, can kill neighbouring bacteria)
4) organic acids
5) low pH
6) nutrient competition

77
Q

what is virulence + where is it present in dental disease

A

pathogenic synergism (mixture of organisms pool their resources to be more virulent)

DENTAL ABCESSES - involve mixtures to overcome host defences + cause tissue damage

78
Q

what does the matrix regulate into/out of the biofilm

A

molecules penetrating readily

organisms going out

79
Q

list properties of the biofilm

A

1) spatially + functionally organised
2) division of labour; multiple interactions [synergistic & antagonistic]
3) r/ship between host environment & microbial composition & activity (host environment influences which organisms are dominant or not)
4) properties of the community = more than the sum of the activities of the individual species

80
Q

which species are present in early stages of biofilm formation

A
  • limited number
  • mainly streptococci
  • mainly aerobic OR facultative anaerobes
81
Q

which species are present in late stages of biofilm formation / MATURE BIOFILM

A
  • diverse community
  • 100 - 300 species harboured
  • MANY obligate anaerobes
  • some ‘unculturable’ species
  • cell-cell associations
  • microbial interactions
    ALL influenced by biology + anatomy of the host
82
Q

what name do we give where round shape bacteria is stuck on the end of a filamentous organism in mature biofilm

A

CORN-COB

83
Q

which staining technique can be used to see structure of dental biofilms

A

FISH (Fluorescent in situ hybridisation)

84
Q

using fish what was discovered about the structure of dental biofilms

A

structurally AND functionally organised

anaerobic organisms at base
aerobic organisms at surface (create the anaerobic environment at the base + metabolic products accumulate here)
BECAUSE more nutrients on surface and high O2 at surface

resilient to change, hard to alter composition bc there are so many interactions + interdependencies between these organisms that its a stable unit

85
Q

list 6 features of multi-species biofilms

A

1) concerted + collaborative metabolism
2) food chains
3) environment modification
4) matrix formation
5) cell-cell signalling
6) complex interactions = balance

86
Q

outline fissure biofilms

because properties of a habitat select the predominant microbes

A
  • streptococci
  • saccharolytic bacteria (CARIES!!)
  • few anaerobes and gram -ves
  • high redox potential
  • neutral - acidic pH
  • influenced by saliva
87
Q

outline gingival crevice biofilms

because properties of a habitat select the predominant microbes

A
  • gram -ve anaerobes
  • spirochaetes + unculturables
  • proteolytic
  • obligately anaerobic
  • low redox potential
  • neutral - alkaline pH
  • influenced by GCF
  • if biofilm not removed regularly = gingivitis and perio disease (lots of anaerobic proteolytic bacteria)
88
Q

there is a DIRECT r/ship between…

A

host, micro-environment + oral microbiota

89
Q

where do we find the most COMPLEX communities

A

gingival crevice

because of many anaerobic organisms

90
Q

which species are harboured in fissure biofilms

A
  • gram +ve

- facultative anaerobes (streptococcus, actinomyces, few gram -ve)

91
Q

which species are harboured in gingival crevice biofilms

A
  • gram +ves & -ves

- obligate anaerobes (streptococcus, actinomyces, eubacterium, fusobacterium, prevotella, spirochaetes, “unculturables”)

92
Q

which species are harboured in approximal biofilms

A
  • gram +ves & -ves

- facultative AND obligate anaerobes (neisseria, streptococcus, actinomyces, prevotella, veillonella)

93
Q

what are properties of dental plaque as a biofilm

A
  • spatial organisation
  • can get altered gene expression (direct & indirect)
  • get increased ‘tolerance’ to antimicrobial agents
  • increased ‘resistnance’ to antimicrobial agents
94
Q

how is increased tolerance to antimicrobial agents conferred in a biofilm

A

when in the structure of a biofilm the organisms are tolerant because not as susceptible (structure of the biofilm protects them) COMPARED TO when theyre freely dispersed and sensitive

95
Q

how is increased resistance to antimicrobial agents conferred in a biofilm

A

gene transfer - 1 organism passes a gene that confers resistance to an antibiotic to another organism

(distinct from standard reduced susceptibility of a biofilm to antimicrobial agents + can happen in biofilms)

96
Q

which 2 antimicrobial resistanve models can be used to measure sensitivity to antimicrobial agents

A

work out

a) MIC (Minimum Inhibitory Concentration - lowest conc that inhibits growth but not necessarily kill)
b) MBC (Minimum Bactericidal Concentration - lowest conc that kills)

97
Q

when chlorhexidine is used to kill streptococcus how many times greater concentration is needed when in a BIOFILM compared to in solution

A

10 - 50

98
Q

what else has been suggested to measure

A

BIC/BKC/BEC (Biofilm Inhibitory, Killing, Erratic Concentration - shows when in biofilm many more times the concentration is required to kill)

only done with a few agents (amine fluoride and chlorhexidine)
1) amine fluoride = 
MBC - 20um 
BIC - 1,500um
2) chlorhexidine
MBC - 5um
BIC - 1,5000um
99
Q

list some other dentally relevant biofilms

and what is the issue with them

A

1) denture plaque
2) dental unit water systems
3) infective endocarditis

carry the SAME issue = a lot more antibiotic required to kill the organisms when in biofilm than solution

100
Q

explain infective endocarditis biofilms

A

bacteria from mouth that get into blood stream colonise + form biofilm on damaged heart valves

101
Q

explain dental unit water system biofilms

A

use agents to prevent build up of biofilms in water spray tubes

102
Q

what does a live dead stain show

A

green = live / viable bacteria

red = dead bacteria

103
Q

in a live dead stain what is apparent when biofilm is exposed to 0.2% chlorhexidine mouthwash

A

chlorhexidine ONLY affects outer layers of biofilm

cannot penetrate as organisms in the biofilm are tolerant of the agent

104
Q

list 4 consequences of plaque as a microbial community

A
  • broader habitat range
    (obligate anaerobes in an overtly aerobic habitat - mouth )
  • inc’d metabolic diversity & efficiency
    (organisms working together to metabolise complex host glycoproteins etc)
  • inc’d tolerance to antimicrobial agents, inhibitors, host defences
  • enhanced pathogenicity
    (pathogenic synergism/polymicrobial disease)
105
Q

explain what cross protection means

A

can treat someone with perio disease with penicillin

organism should be sensitive to it

BUT if organism in the community produces β-lactamase this breaks penicillin down protecting our target organism

106
Q

what can major ecological pressure be caused by and what does this affect

A

diet, saliva flow reduction due to medication / age

alters microbe balance breaking down microbial homeostasis
leads to outgrowth of pathogens and we get disease - DYSBIOSIS

107
Q

list immunological factors responsible for breakdown of microbial homeostasis (dysbiosis)

A
  • neutrophil dysfunctions
  • suppression of host defences
  • sIgA-deficiency
  • chemotherapy induced myelosuppression (= bone marrow suppression)
  • infection induced myelosuppression (ie AIDS)
108
Q

list non-immunological factors responsible for breakdown of microbial homeostasis (dysbiosis)

A
  • antibiotics inhibit beneficial organism
  • sugary diet (= low pH)
  • medication affecting salivary flow
  • xerostomia
  • increased GCF flow (due to oral contraceptives)
109
Q

what are plaque mediated diseases often due to

A
  • change in local environment
  • disruption of homeostasis (natural balance between us + our microbes in which minor components of the oral microbial community suddenly get a benefit)
  • enrichment of minor bacterial popoulations

IOE - microbiology (5 decks)

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