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IOE - microbiology > mouth as a microbial habitat > Flashcards

mouth as a microbial habitat Flashcards

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1
Q

what does the resident human microbiota refer to

A

the complete collection of organisms present at a particular body site

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2
Q

microbes are considered to be

A

a microbial community / consortium

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3
Q

define the human microbiome

A

all organisms associated with the human body and genetic material

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4
Q

define microbial habitat

A

site where microorganisms grow and microbes found in a specific habitat together with its living and non-living surroundings make up an ecosystem

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5
Q

how do scientists characterise microbes living on/in us

A

find ways to identify them ie what species are found in what body sites
name them by heterogenous level / species level

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6
Q

technological advances have enabled scientists to…

A

determine with more reliable methods the species of microbes present
AND what genes / proteins are being expressed

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7
Q

what does phyla refer to

A

taxonomy so which species / organism in terms of the identification

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8
Q

what are metabolic pathways (ie of plaque)

A

what genes, amino acids and proteins are being expressed by organisms present

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9
Q

what are the characteristics of streptococcus mutans (caries causing)

A

produce strong acid and survive in low pH

SO a high abundance of these gives rise to caries

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10
Q

how many cells make up the human body

A

~10^14 (100 trillion)

only 10% are of human origin (remainder = microbial)

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11
Q

what was microbial composition previously thought to be

A

10x more than number of cells

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12
Q

what causes variation in microbial composition

A

varies between individuals

varies depending on rhythm (morning, afternoon, evening)

it changes within the same body sites (ie gut microbes change depending on if individual has been to the toilet or not)

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13
Q

what is the microbial load in the mouth

A

10^7 bacteria per site (10 million)

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14
Q

what is the microbial load in 1ml of saliva

A

10^8 (100 billion microbes)

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15
Q

what are the most abundant type of microbes

A

bacteria (though viruses, fungi, protozoa may be present)

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16
Q

how many species / type of organism have been identified in the human mouth

A

1000+

they grow within biofilms

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17
Q

at any one time how many different types of species are found in the mouth

A

~4500

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18
Q

give the 2 main oral disease caused by dental plaque

A

caries

periodontitis

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19
Q

what proportion of the population do caries affect in most countries

A

nearly 100%

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20
Q

what proportion of 5 year olds in England suffer from tooth decay

A

1/3

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21
Q

give the figure spent by the NHS on hospital tooth extractions in 2012-13

A

£30 million

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22
Q

what is the correlation between caries and hospital admission in 5-9 year olds in England

A

most common cause of admission

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23
Q

give the figure of how many under 18s were admitted to hospital for extraction because of caries in 2014-15

A

42,037

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24
Q

what further problems are frequently caused by oral infections

A

abscesses and painful sinuses requiring antibiotic treatment

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25
Q

severe periodontitis…

A

is 6th most prevalent disease worldwide

shares common risk factors with other systemic diseases ie heart disease, diabetes, obesity, rheumatoid arthritis, cancer and to pre-term low birth weights

affects 2-20% of most adult populations

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26
Q

oral infections affect how many people worldwide

A

300 million

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27
Q

how many suffer with advanced periodontitis in the UK and how much does this cost the NHS per year

A

3-4 million

2 BILLION

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28
Q

which 4 types of organism inhabit the mouth

A

1) eukaryotes
2) prokaryotes
3) viruses
4) prions

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29
Q

briefly overview eukaryotes

A

human cells are eukaryotic and we are complex multicellular organisms

includes fungi (have a higher level of organisation than bacteria
or prokaryotes) and protozoa

10-100um

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30
Q

briefly overview prokaryotes

A

the archaebacteria = share many characteristics of eubacteria and include some organisms that are able to survive the most extreme habitats

includes bacteria (most abundant type found in mouth) and eubacteria

1 - 10 um

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31
Q

briefly overview viruses

A

non-cellular because they are made of nucleic acid (rna OR dna) enveloped by a protective protein coat (rather than phospholipid membrane like cells)

they ARE considered living organisms

rely on intracellular machinery of other cells to
synthesise their matter and ensure their propagation and dispersal

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32
Q

briefly overview prions

A

combination of proteins and infection (they are types of proteins which induce normal cellular proteins to fold abnormally)

some evidence
of the transmissibility from oral tissues of prions

they are causative agents of spongiform encephalopathies and affect the brain and nervous systems of many animals

almost considered a living organism

considered non-cellular

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33
Q

give an example of a prion disease

A

“mad cow disease” - bovine spongiform encephalopathy

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34
Q

what is taxonomy

A

branch of science concerned with classification of organisms

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35
Q

define classification

A

arrangement into taxonomic groups based on similarities / relationships

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36
Q

define nomenclature

A

assignment of names to groups according to international rules (ie genus and species)

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37
Q

define identification

A

determining the group or taxon to which new isolates belong

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38
Q

give the 8 taxonomic ranks in order

A

1) kingdom
2) division
3) sub-division
4) order
5) family
6) genus
7) species
8) strain

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39
Q

give the taxonomy for streptococcus mutans

A

1) procaryotae
2) firmicutes
3) low G+C DNA
4) NO order
5) streptococcaceae
6) streptococcus
7) streptococcus mutans
8) S. mutans NCTC 10449

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40
Q

why do why sub-classify species into strains

A

because different strains have different specific genes that confer virulence on us

eg E. coli -> present in everyones gut (most commonly GI tract) and some types give bloody diarrhea etc

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41
Q

define plaque

A

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

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42
Q

what is plaque matrix

A

sticky substance produced by microbial community

helps with adhesion

some bacteria use it as a source of nutrients

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43
Q

define commensals

A

organisms considered members of resident oral microbiota and naturally found on/in the body

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44
Q

why are commensals advantageous to us

A

we’ve co-evolved with them

they occupy specific niche and habitat on and in us

their presence serves as antagonism of exogenous pathogens preventing their colonisation as the habitat is filled with commensals which help fight them off (competitive exclusion of exogenous pathogens)

45
Q

what are exogenous pathogens

A

pathogens coming from outside of the body / the environment

46
Q

what 2 things does the oral microbiota promote

A

1) normal development of immune system = we are immediately colonised by microbes when born
2) normal human cellular physiology and nutrition -> especially in the gut (microbiota helps us to digest)

47
Q

what 2 things does the oral microbiota enhance

A

1) epithelial barrier function

2) cellular proliferation + wound healing responses

48
Q

what is the role of certain important resident symbiotic bacteria

A

actively modulate immunity to prevent chronic over stimulation

49
Q

what would follow if the microbiota became dis-regulated or imbalanced

A

disease

50
Q

why is the mouth ecologically distinctively unique from other body sites?

A

warm
moist
specific pH
there are numerous sites within the mouth that offer different environments and surfaces

51
Q

why is there different microbial profile / composition in infants born through C-section and naturally and
what happens with time

A

because from birth we are immediately colonised

it stabilises becoming richer and more similar to what it should be

52
Q

what surfaces are present for the first few months of life and what happens to these

A

mucosal (cheeks, palate, lips) which are colonised by microbes

when teeth appear these new surfaces are also colonised

53
Q

give 4 features of the mouth which provide different environments

A

1) mucosal surfaces
2) teeth
3) saliva
4) GCF

54
Q

why does microbial load on mucosal surface remain relatively low

A

due to the process of desquamation (shedding of outer layer of epithelium)

55
Q

why is the structure of the dorsum of the tongue unique

A

papillary structure provides refuge to many microbes normally washed off through mastication and salivary flow

microbes and food debris can get stuck thus it provides a resevoir for microbial colonisation

even if you scrape the tongue you’ll never reach all microscopic areas colonised by biofilms and microbes

56
Q

what do teeth provide for microbial colonisation and what does this lead to

A

non-shedding surfaces

accumulation of dental plaque leading to caries, gingivitis, periodontitis

57
Q

what occurs at different tooth sites / surfaces

A

variation in conditions which attract different types of microorganisms

58
Q

which 2 components of the oral cavity have influence on the oral microbiota and why

A

saliva and GCF

due to their composition

59
Q

describe the composition of saliva

A

99% water

rest = proteins, inorganic molecules, lipids, hormones

60
Q

where is saliva produced

A

parotid, sub-mandibular and sub-lingual glands

61
Q

what are the functions of saliva

A

mastication, taste, digestion, lubrication

buffering role = protects the teeth from demineralisation by promoting remineralisation

important for oral health

62
Q

what is the composition of GCF

A

serum like fluid / exudate

phagocytic cells

Contains complements of the host defences

63
Q

where is GCF found

A

junctional epithelium of gingiva

64
Q

what is the flow rate of GCF

A

slow at healthy sites
BUT
increases in conditions of gingivitis and periodontal disease and temperature increases too

these variations in conditions impact type of organisms living in the habitat

65
Q

list the 7 factors which influence colonisation and survival

A

1) temperature
2) redox potential / O2 concentration
3) nutrients + pH
4) host defences
5) host genetics and lifestyle
6) saliva
7) mucosal defences

66
Q

what temperature is the oral cavity

A

30-36 degrees

67
Q

what temperature is the mouth

A

30 degrees

68
Q

what does a stable temperature allow

A

growth of many microbes

69
Q

what happens when inflammation occurs

A

you get a temperature which microorganisms display sensibility to

70
Q

what is redox

A

reductions and oxidation

71
Q

how is the redox of a substance defined

A

the ease by which it loses (is oxidised) / gain electrons (is reduced)

72
Q

how does redox potential influence types of organisms living in a particular site

A

depends on its level

73
Q

which 2 sources can nutrients come from

A

1) endogenous

2) exogenous

74
Q

what are edogenous nutrients

A

internal sources (compounds produced within our mouths)

75
Q

what are exogenous nutrients

A

external sources

76
Q

what pH do most organisms prefer to grow

A

between 6.75 and 7.25

77
Q

what happens to plaque pH after carbohydrate consumption

A

falls rapidly to below 5 because of metabolic activity of the organism that used the sugar producing acid as a waste product

78
Q

what happens with frequent sugar intake

A

constant source of nutrient for the microorganism so acid is constantly produced changing the pathonation of the microbiota and promoting those who thrive in these conditions (ie S. mutans)

79
Q

why do nutrients affect colonisation and survival

A

many are nutritionally demanding and have specific requirements for nutrients

80
Q

what do host defences do

A

first line of defence against microorganisms acting as a physical barrier to invasion of microbes

81
Q

what is the additional defence mechanism that exists to maintain health divided into

A

innate and adaptive immunity

82
Q

what does the health of the mouth depend on

A

integrity of the mucosa and enamel

83
Q

what is innate immunity

A

doesn’t require previous exposure to microorganism

provides broad spectrum protection (eg musin, agglutinins, lysozyme)

defends mouth against invasion of microorganism

84
Q

what is adaptive immunity

A

immunity that occurs after exposure to an antigen (ie from a pathogen or vaccination) and antibodies etc are produced

activated when the innate response is insufficient to control an infection

85
Q

how can host genetics influence disease susceptibility

A

Certain ethnic groups and each gender have distinct microbial signatures

86
Q

what are found only in certain ethnic groups

A

carriers of specific bacterial species / specific serotypes of organism

87
Q

how can lifestyle affect personal microbiome

A

diet, smoking, medication etc can increase risk of caries

88
Q

what roles does saliva have in maintaining oral health

A

delivers components of innate and adaptive host responses to regulate microbial colonisation

mainly IgA immunoglobulins present

89
Q

which immunoglobulins are present in GCF

what else does GCF contain

A

mainly IgG but also IgA and IgM

leukocytes = 95% are neutrophils

90
Q

what are mucosal defences

A

physical defences ie desquamation as act as a physical barrier

91
Q

when are mucosal defences immunological

A

when presence of bacteria induces cells to release signalling molecules (chemokines + cytokines) which lead to reduction of microbial load maintaining balance

92
Q

what are signalling molecules produced by

A

polymorphonuclear leukocytes

93
Q

define the “resident / indigenous” or “normal

microflora” / “normal microbiota”

A

the populations that colonise a human host

94
Q

what do we refer to all of the organisms that colonise

the human body as

A

the human microbiome

95
Q

what is host-microbe homeostasis

A

where host and microbes reach a balanced state in which health is maintained

96
Q

what advantages do resident populations confer to us as hosts

A

1) occupy sites so they cannot be colonised by external pathogens
2) promote development of the immune system and normal cell function

97
Q

define biofilm

A

communities of
bacteria adhered to a surface and embedded within an extracellular matrix of
microbial and host origin

98
Q

why is growth in a biofilm significant

A

bacteria are better able to tolerate antimicrobial agents and the host defences

99
Q

which archaebacteria
are found in the mouth

what do they require

A

methanogenic = methane producing

H2S producing = sulphate reducing

extremely anaerobic environments

100
Q

what are fungi

A

eukaryotic, multinucleate or multicellular organisms with a thick cell wall

101
Q

which fungi growth forms are responsible for

most human disease

A

those that grow as branches filaments (many hyphae form a
mycelium; eg. Aspergillus)

or as yeasts (ie candida) which are single celled and reproduce by budding

102
Q

what can candida be induced to form

A

hyphae (“germ-tube formation”)

103
Q

what can candida cause in some individuals

A

disease ie thrush

esp when oral ecology is disrupted because of administration of antibiotics or if an individual is
immunocompromised

can colonise dentures

104
Q

what are protozoa

A

diverse group of eukaryotic organisms

usually unicellular

exhibit great variety of structures and life-styles

105
Q

what size are protozoa

A

1um - several mm

106
Q

where are protozoa found

A

mostly aerobic and free living (soil, water)

some grow anaerobically or microaerophilically (in presence of sub-atmospheric O2 levels)

107
Q

which protozoa species have been isolated in the mouth

A

Entamoeba gingivalis

Trichomonas

tenax

Giardia lamblia

(their prevalence/importance in the oral cavity = unclear)

108
Q

what are viral particles called

A

virions

109
Q

give some morphological types of bacteria

A

rods
cocci
curved
spiral

IOE - microbiology (5 decks)

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