Week 8 Flashcards
Define symbiosis
To live together in a relationship which is mutually beneficial to the host and the microbe, or harmful to the host.
Define mutualism
Both members benefit from the symbiotic relationship and in some cases need each other for survival.
Define commensalism
One of the organisms in he symbiotic relationship benefits without affecting the other.
Define parasitism in terms of symbiosis.
A parasite benefits from its host without harming it
What type of relationships do microbiota in the normal flora have with the body?
Mutualistic and commensal
How many different types of microbiota are in the normal human flora?
400-1000
What are the 2 types of Indigenous microbiota?
Resident microbiota
Transient microbiota
What are indigenous microbiota?
They reside inside the body but rarely cause disease.
What are resident microbiota?
They are specially adapted t live in the body and are unique to each individual.
What is the main function of resident bacteria?
Compete out foreign bacteria.
How long can transient microbiota survive in the body for ?
Hours to months
Why can’t transient microbiota survive in the body long term?
There is alot of competition from other microorganisms.
They are often eliminated by the body’s immune system.
Affected by chemical and physical changes in the body.
What are opportunistic pathogens?
An infection caused by a pathogen that takes advantage of an opportunity that is not usually available.
Give examples of circumstances which may allow opportunistic pathogens to cause disease.
Immune suppression
Changes in normal microbiota
Incorrect location
Describe the presence of microbiota in the nose
Very unique microbiota because it is cooler than the rest of the respiratory system.
Describe the presence of microbiota in the trachea and bronchi
Sparse
Describe the presence of microbiota in the alveoli
No microbiota present
Describe the presence of microbiota in the vagina
Change as acidity changes in the vagina during the menstruations cycle.
Why can’t extensive colonisation of microbiota occur at the urethra?
The flow of urine prevents this
Why are there few microbiota in the eyes compared to the skin?
They are washed away by tears.
What prevents a foetus having any microbiota?
The presence of the amniotic fluid and use of the mothers immunity.
When the amniotic sac breaks, how does microbiota enter a baby?
Enters the mouth and nose of the baby via the birth canal.
At what stage can microbiota begin to enter the intestines of a baby?
Once it has consumed its first meal.
How quickly are resident microbiota established on a human body?
Within the first months of life
Define Pathogenicity
The ability to cause disease
Define Virulence
A measure of pathogenicity
Define contamination
The mere presence of microorganisms in or on the body.
Define infection
Invasion of the body by a pathogen
Define pathogen
A microorganism with the ability to cause disease.
What are virulence factors?
A variety of traits that interact with a host and enable the pathogen to enter, adhere, gain access to nutrients and escape detection from the immune system.
What are the events of infection?
Exposure to the pathogen.
Adhere to skin or mucosa.
Invasion through epithelium.
Colonisation and growth.
Tissue damage and disease.
What are the possible portals of entry on the human body for a microorganism?
Broken skin Insect bite site Anus Urethra Vagina / Penis Placenta Mouth Nose Conjuctiva of eye Ear
What are the main portals of entry for microbiota on the human body?
Mucous membranes
What parts of the human body do mucous membranes cover?
All exposed body cavites
What is meant by ‘adhesion’ in terms of macrobiotic infection?
Attachment to cells
What are adhesions in bacteria?
Surface lipoproteins or glycoproteins the bin to host cell receptors.
What type of molecule on the surfaces of microbiomes bind to host cells?
Lipoproteins or glycoproteins
Where are adhesions in bacteria found?
In the Fimbriae and flagella
What is created when bacteria colonise at a site?
A biofilm
What is used to carry out invasion by microbiomes?
Extracellular enzymes or toxins
What are the 2 categories of toxins?
Exotoxins and endotoxins
Outline how Hyaluronidase and Collagenase enzymes invade host cells
Bacteria reach the epithelial surface of the host cells and release Hyaluronidase and Collagenase. These cause the epithelial cells to move apart and allow bacteria to invade deeper into the cell.
Explain how bacteria use Coagulase and Kinase to aid infection.
Bacteria produce Coagulase which causes a clot to form on the edge of blood vessels. Bacteria then produce Kinase which dissolves the clot and releases bacteria into the blood stream.
What are bacterial exotoxins?
They are secreted by the bacterial cell wall
Give examples of bacterial exotoxins.
Cytotoxins
Neurotoxins
Enterotoxins
What are bacterial endotoxins?
They are part of the bacterial cell all.
Give an example of a bacterial endotoxin
LIPID A
How do exotoxins from bacteria cause issues with host cells?
They directly kill host cells
How do endotoxins from bacteria cause issues within host cells?
They induce effects such as fever, inflammation, diarrhoea, shock and blood coagulation.
What is required for colonisation and growth of bacteria which have invaded a host?
Antiphagocytic factors
Give examples of antiphagocytic factors
Capsules
Antiphagocytic chemicals
What does the host’s immune system use to fight invading microbiomes?
Phagocytes
What is a capsule?
A layer of polysaccharide around a bacterial cell.
Why do the capsules of Bacteria not trigger an immune response from host cells?
They have the same polysaccharides in their capsule as are found in the body naturally.
What virulence factors are associated with exposure of the host to a pathogen during infection?
None
What virulence factors are associated with adherence to skin or mucosa during infection?
Adhesins and biofilms
What virulence factors are associated with invasion through epithelium during infection?
Extracellular enzymes and toxins
What virulence factors are associated with colonisation and growth during infection?
Capsules and anti-phagocytic chemicals
What are symptoms of disease?
They are subjective but frequently cause nausea.
What are the signs of disease?
They are objective but can often be measured.
e.g. vomitting
What is meant by the term ‘syndrome’?
A group of signs and symptoms.
What are the stages of infectious disease?
Incubation period. Prodromal period. Illness Decline Convalescence
What is the incubation period of an infectious disease?
There are no signs and symptoms of the disease
What does the length of the incubation period of an infectious disease depend on?
Virulence of pathogen.
Infective disease.
Host immunity.
Site of infection.
What is the incubation period of influenza ?
About 1 day
What is the incubation period of AIDS?
1-8 years
What is the incubation period of leprosy?
10 to 30 years
How long does the prodromal period of an infectious disease last?
Short time
What are the generalised symptoms of the prodromal stage of an infectious disease?
Malaise and muscle ache
What is Malaise?
General feelings of discomfort or illness of which the exact cause is difficult t identify.
Do all infections have a prodromal period?
No
What is the most severe stage of infectious disease?
Illness
What is happening during the ‘illness’ stage of an infectious disease?
The signs and symptoms are most evident and the patients immune system has not fully responded yet.
What happens during the decline phase of infectious disease?
The patients body return to normal as the immune response or medical treatment defeats the pathogen.
This causes symptoms to subside.
In what stage of infection does the immune response peak ?
During define
What is the ‘convalescence’ period of infection?
The patient recovers and tissues are repaired.
What determines the length of time that the convalescence period of infection lasts?
Amount of damage caused.
Nature of the pathogen.
Site of infection.
Overall well-being of the patient.
