mouth as a microbial habitat Flashcards
(109 cards)
1
Q
what does the resident human microbiota refer to
A
the complete collection of organisms present at a particular body site
2
Q
microbes are considered to be
A
a microbial community / consortium
3
Q
define the human microbiome
A
all organisms associated with the human body and genetic material
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
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
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
7
Q
what does phyla refer to
A
taxonomy so which species / organism in terms of the identification
8
Q
what are metabolic pathways (ie of plaque)
A
what genes, amino acids and proteins are being expressed by organisms present
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
10
Q
how many cells make up the human body
A
~10^14 (100 trillion)
only 10% are of human origin (remainder = microbial)
11
Q
what was microbial composition previously thought to be
A
10x more than number of cells
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)
13
Q
what is the microbial load in the mouth
A
10^7 bacteria per site (10 million)
14
Q
what is the microbial load in 1ml of saliva
A
10^8 (100 billion microbes)
15
Q
what are the most abundant type of microbes
A
bacteria (though viruses, fungi, protozoa may be present)
16
Q
how many species / type of organism have been identified in the human mouth
A
1000+
they grow within biofilms
17
Q
at any one time how many different types of species are found in the mouth
A
~4500
18
Q
give the 2 main oral disease caused by dental plaque
A
caries
periodontitis
19
Q
what proportion of the population do caries affect in most countries
A
nearly 100%
20
Q
what proportion of 5 year olds in England suffer from tooth decay
A
1/3
21
Q
give the figure spent by the NHS on hospital tooth extractions in 2012-13
A
£30 million
22
Q
what is the correlation between caries and hospital admission in 5-9 year olds in England
A
most common cause of admission
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
24
Q
what further problems are frequently caused by oral infections
A
abscesses and painful sinuses requiring antibiotic treatment
25
severe periodontitis...
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
26
oral infections affect how many people worldwide
300 million
27
how many suffer with advanced periodontitis in the UK and how much does this cost the NHS per year
3-4 million
2 BILLION
28
which 4 types of organism inhabit the mouth
1) eukaryotes
2) prokaryotes
3) viruses
4) prions
29
briefly overview eukaryotes
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
30
briefly overview prokaryotes
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
31
briefly overview viruses
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
32
briefly overview prions
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
33
give an example of a prion disease
"mad cow disease" - bovine spongiform encephalopathy
34
what is taxonomy
branch of science concerned with classification of organisms
35
define classification
arrangement into taxonomic groups based on similarities / relationships
36
define nomenclature
assignment of names to groups according to international rules (ie genus and species)
37
define identification
determining the group or taxon to which new isolates belong
38
give the 8 taxonomic ranks in order
1) kingdom
2) division
3) sub-division
4) order
5) family
6) genus
7) species
8) strain
39
give the taxonomy for streptococcus mutans
1) procaryotae
2) firmicutes
3) low G+C DNA
4) NO order
5) streptococcaceae
6) streptococcus
7) streptococcus mutans
8) S. mutans NCTC 10449
40
why do why sub-classify species into strains
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
41
define plaque
the community of microorganisms found on the tooth surface as a biofilm embedded in a matrix of polymers of salivary and bacterial origin
42
what is plaque matrix
sticky substance produced by microbial community
helps with adhesion
some bacteria use it as a source of nutrients
43
define commensals
organisms considered members of resident oral microbiota and naturally found on/in the body
44
why are commensals advantageous to us
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
what are exogenous pathogens
pathogens coming from outside of the body / the environment
46
what 2 things does the oral microbiota promote
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
what 2 things does the oral microbiota enhance
1) epithelial barrier function
| 2) cellular proliferation + wound healing responses
48
what is the role of certain important resident symbiotic bacteria
actively modulate immunity to prevent chronic over stimulation
49
what would follow if the microbiota became dis-regulated or imbalanced
disease
50
why is the mouth ecologically distinctively unique from other body sites?
warm
moist
specific pH
there are numerous sites within the mouth that offer different environments and surfaces
51
why is there different microbial profile / composition in infants born through C-section and naturally and
what happens with time
because from birth we are immediately colonised
it stabilises becoming richer and more similar to what it should be
52
what surfaces are present for the first few months of life and what happens to these
mucosal (cheeks, palate, lips) which are colonised by microbes
when teeth appear these new surfaces are also colonised
53
give 4 features of the mouth which provide different environments
1) mucosal surfaces
2) teeth
3) saliva
4) GCF
54
why does microbial load on mucosal surface remain relatively low
due to the process of desquamation (shedding of outer layer of epithelium)
55
why is the structure of the dorsum of the tongue unique
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
what do teeth provide for microbial colonisation and what does this lead to
non-shedding surfaces
accumulation of dental plaque leading to caries, gingivitis, periodontitis
57
what occurs at different tooth sites / surfaces
variation in conditions which attract different types of microorganisms
58
which 2 components of the oral cavity have influence on the oral microbiota and why
saliva and GCF
due to their composition
59
describe the composition of saliva
99% water
rest = proteins, inorganic molecules, lipids, hormones
60
where is saliva produced
parotid, sub-mandibular and sub-lingual glands
61
what are the functions of saliva
mastication, taste, digestion, lubrication
buffering role = protects the teeth from demineralisation by promoting remineralisation
important for oral health
62
what is the composition of GCF
serum like fluid / exudate
phagocytic cells
Contains complements of the host defences
63
where is GCF found
junctional epithelium of gingiva
64
what is the flow rate of GCF
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
list the 7 factors which influence colonisation and survival
1) temperature
2) redox potential / O2 concentration
3) nutrients + pH
4) host defences
5) host genetics and lifestyle
6) saliva
7) mucosal defences
66
what temperature is the oral cavity
30-36 degrees
67
what temperature is the mouth
30 degrees
68
what does a stable temperature allow
growth of many microbes
69
what happens when inflammation occurs
you get a temperature which microorganisms display sensibility to
70
what is redox
reductions and oxidation
71
how is the redox of a substance defined
the ease by which it loses (is oxidised) / gain electrons (is reduced)
72
how does redox potential influence types of organisms living in a particular site
depends on its level
73
which 2 sources can nutrients come from
1) endogenous
| 2) exogenous
74
what are edogenous nutrients
internal sources (compounds produced within our mouths)
75
what are exogenous nutrients
external sources
76
what pH do most organisms prefer to grow
between 6.75 and 7.25
77
what happens to plaque pH after carbohydrate consumption
falls rapidly to below 5 because of metabolic activity of the organism that used the sugar producing acid as a waste product
78
what happens with frequent sugar intake
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
why do nutrients affect colonisation and survival
many are nutritionally demanding and have specific requirements for nutrients
80
what do host defences do
first line of defence against microorganisms acting as a physical barrier to invasion of microbes
81
what is the additional defence mechanism that exists to maintain health divided into
innate and adaptive immunity
82
what does the health of the mouth depend on
integrity of the mucosa and enamel
83
what is innate immunity
doesn’t require previous exposure to microorganism
provides broad spectrum protection (eg musin, agglutinins, lysozyme)
defends mouth against invasion of microorganism
84
what is adaptive immunity
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
how can host genetics influence disease susceptibility
Certain ethnic groups and each gender have distinct microbial signatures
86
what are found only in certain ethnic groups
carriers of specific bacterial species / specific serotypes of organism
87
how can lifestyle affect personal microbiome
diet, smoking, medication etc can increase risk of caries
88
what roles does saliva have in maintaining oral health
delivers components of innate and adaptive host responses to regulate microbial colonisation
mainly IgA immunoglobulins present
89
which immunoglobulins are present in GCF
| what else does GCF contain
mainly IgG but also IgA and IgM
| leukocytes = 95% are neutrophils
90
what are mucosal defences
physical defences ie desquamation as act as a physical barrier
91
when are mucosal defences immunological
when presence of bacteria induces cells to release signalling molecules (chemokines + cytokines) which lead to reduction of microbial load maintaining balance
92
what are signalling molecules produced by
polymorphonuclear leukocytes
93
define the "resident / indigenous" or “normal
| microflora” / "normal microbiota”
the populations that colonise a human host
94
what do we refer to all of the organisms that colonise
| the human body as
the human microbiome
95
what is host-microbe homeostasis
where host and microbes reach a balanced state in which health is maintained
96
what advantages do resident populations confer to us as hosts
1) occupy sites so they cannot be colonised by external pathogens
2) promote development of the immune system and normal cell function
97
define biofilm
communities of
bacteria adhered to a surface and embedded within an extracellular matrix of
microbial and host origin
98
why is growth in a biofilm significant
bacteria are better able to tolerate antimicrobial agents and the host defences
99
which archaebacteria
are found in the mouth
what do they require
methanogenic = methane producing
H2S producing = sulphate reducing
extremely anaerobic environments
100
what are fungi
eukaryotic, multinucleate or multicellular organisms with a thick cell wall
101
which fungi growth forms are responsible for
| most human disease
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
what can candida be induced to form
hyphae (“germ-tube formation”)
103
what can candida cause in some individuals
disease ie thrush
esp when oral ecology is disrupted because of administration of antibiotics or if an individual is
immunocompromised
can colonise dentures
104
what are protozoa
diverse group of eukaryotic organisms
usually unicellular
exhibit great variety of structures and life-styles
105
what size are protozoa
1um - several mm
106
where are protozoa found
mostly aerobic and free living (soil, water)
some grow anaerobically or microaerophilically (in presence of sub-atmospheric O2 levels)
107
which protozoa species have been isolated in the mouth
Entamoeba gingivalis
Trichomonas
tenax
Giardia lamblia
(their prevalence/importance in the oral cavity = unclear)
108
what are viral particles called
virions
109
give some morphological types of bacteria
rods
cocci
curved
spiral
