The Mouth As A Microbial Habitat Flashcards
What is microbiology
The study of microorganism
What are microorganisms?
Organisms too small to see with the naked eye
What does the resident microbiota refer to?
The complete collection of organisms at a specific body site
What is the human microbiome?
The complete collection of organisms at a specific body site and also includes the totality of material that these microbes have ie includes genetic material
How many cells is the human body made up of?
More than 10^14
100,000,000,000,000
What are the 6 main microbial communities in the body?
Mouth Skin Axilla Stomach Intestine UG tract
How many bacteria cells are there in the mouth and saliva?
10^7 bacterial sites
10^8 per ml of saliva
Grand total is approx 10^10 (10,000,000,000)
How many bacteria cells are there on the skin?
10^12 over the body surface
1,000,000,000,000
How many bacteria cells are there in the intestine?
10^8 - 10^12 Bacteria per gram of faeces
How many bacteria cells are there in the UG tract?
Ranges from sterile in the bladder to densely populated in the vagina and urethra
Describe the microbial community in the stomach
Sparsely populated
How many specifies of bacteria are there in the human mouth
1000 in total
But on average each individual carries 300-500 bacterial species
What are caries and periodontal disease caused by?
Dental plaque that is composed of mainly bacteria and their extracellular matrix
How many people were affected by caries?
100% of the population
How much does dental caries in children cost?
More than $3500 per 100 children
How many children in the uk suffer from tooth decay
Around 1/3 of 5 year old children
How many children and young adults were admitted to hospital in England (2014-2015) for extraction of teeth due to caries?
42,037
What is the most common cause for hospital admission of children between the ages of 5-9?
Dental caries
How much was spent by the NHS on hospital based tooth extraction on children in 2012
£30 million
What can tooth decay lead to?
Development of abscesses and sinuses that are painful and require antibiotic treatments
How much of the population suffered from periodontitis?
2-20% of most adult populations
How many people world wide are affected by periodontitis?
300 million
It’s the 6th most prevalent infectious disease
In the UK how many people suffer from advanced periodontitis and how much does this cost the NHS?
3-4 million currently suffering
Costs NHS £2 billion every year
Which systemic diseases are linked with periodontitis
Cardiovascular diseases Diabetes Obesity Rheumatoid arthritis Cancer Alzheimer’s
Name the 4 types of microorganisms found in the mouth
Eukaryotes
Prokaryotes
Viruses
Prions
Give an example of and state the length of eukaryotes
E.g. fungi like yeast that causes thrush, Protozoa like Plasmodium that causes malaria
10-100 micrometers
Give an example of and state the length of prokaryotes
E.g. Eubacteria, archbacteria
1-10 micrometers
What are viruses and how big are they?
They are acellular
50-100 nm
What are prions and how big are they
They are non cellular
5-10 nm
What is the debate surrounding prions?
Some people debate they are not considered as living elements
They are proteins that cause infections
They can reproduce but how
Why are viruses described as a cellular
Because a cellular organisms possesses a phospholipid membrane but virus is an entity made up of nucleic acid and the genetic material is found in a protein capsule
What is taxonomy
It is a branch of science that’s concerned with the classification of organisms
Define nomenclature
Assignment of names to groups according to international rules
Define identification in relation to taxonomy
Determining group/ taxon to which new isolates belong to
What is classification in taxonomy?
The arrangement of organisms into taxonomic groups based on similarities or relationships
What is plaque?
The community of microorganisms found on the tooth surface as a biofilm embedded in a matrix of polymers of salivary and bacterial origin
Plaque is a biofilm
What are the different taxonomic groups?
Kingdom Division Sub division Order Family Genus Species Strain
What are some of the benefits of the resident human microbiota
Competitive exclusion of exogenous pathogens
Antagonism of exogenous pathogens
Promotion of normal development of the immune system
Promotion of normal human cellular physiology and nutrition
Enhancement of cellular proliferation and wound healing responsible
Enhancement of epithelial barrier function
Certain important symbiotic bacteria actively modulate immunity to prevent chronic over stimulation (tolerance)
Disease follows dis regulation or imbalance
What are some distinct sites for colonisation in the mouth?
Mucosal surfaces
Teeth
Saliva
Gingival crevicular fluid
How is the mouth distinct from the rest of the body
It is moist
Warm
It has very specific pH at different sites of the mouth
There are different environments and surfaces
When are we first colonised by microbes
As soon as we enter the birth canal
How are mucosal surfaces a distinct site for colonisation?
Mucosal surfaces are similar to those in digestive tract
The microbial loaf remains relatively low due to a process called desquamation
What is desquamation
Shedding of the outer layer of the epidermis
How does the tongue provide a unique site for colonisation?
The papillary structure can offer a different kind of habitat as compared to the lips mucosal surfaces of the cheeks etc
Provides refuge to some microbes that may have been washed away by swallowing or mastication
How do teeth provide a distinct site for colonisation
They provide non shedding surfaces which allows for the acclimation if plaque
Which part of the mouth is keratinised?
The gingiva and hard palate
Which part of the mouth is non-keratinised?
Cheeks lips and soft palate
Give examples of different types and plaque and how are they caused?
Fissure plaque: exposed to more oxygen and salivary flow
Gingival crevice plaque: access to a lot less oxygen
There’s variation in the environmental conditions at different sites resulting in different plaques formation as different bacteria can survive in different environments
What is saliva produced by?
Major glands:
Parotid submandibular sublingual glands
Minor glands associated with the mucosa
What is the saliva made up of?
99% water
1% is made up of proteins, glycoproteins inorganic components, lipids, hormones
What are some of the major roles of saliva?
Mastication Taste Lubrication Digestion Proximities remineralisation of teeth Acts as a buffer
What is the buffering when in saliva called?
Bicarbonate
What is gingival crevicular fluid (CGF)
It is a serum like exudate
Viscous fluid which has a similar composition to serum
Slow rate of GCF at healthy site
In case of inflammation GCF rate increases
What do both saliva and GCF contain?
Components of the host defences
What factors influence colonisation and survival
Temperature (35-36°C) Redox potential Oxygen concentration PH (mean pH of saliva 6.75-7.25) Nutrients (endogenous and exogenous) Host defence (dependent on the integrity of the enamel and mucosa) Host genetics Host lifestyle
What is redox potential?
The redox potential of a substance fluid or molecule is defined as the ease by which the substance gains or loses electrons
What is the gain of electrons called
Reduction
What is the loss of electrons called
Oxidation
What does endogenous mean?
Comes from within us like proteins to make enzymes etc
What does exogenous mean?
Coming from the outside ie from your diet
What are the first line of defence of microbes in the mouth
The enamel and mucosa
What is the predominant Immunoglobulin found in saliva
Immunoglobulin A
IgA
What is the predominant Immunoglobulin found in GCF
Immunoglobulin G
IgG
Name some factors influencing colonisation and survival
Saliva
Gingival crevicular fluid
Mucosal defences
What are the mucosal defenders
Physical barrier including desquamation
Immunological defences where the presence of bacteria will make us release signalling molecules that are produced by polymorphonuclear lymphocytes these molecules help reduce the bacterial load that has activated the signalling
Give some features of the mouth
It is a hostile environment
Very selective
Has a complex array of just response
Has a rich oral microbiota
