Wk 13 - Medical Microbiology Flashcards
Whats the difference between an infectious disease and a disease caused by a microme?
Inf disease can be transmitted and there is an action between hosts.
Disease can be caused by own normal flora which is not necessarily transmissable.
Name some organisms with a strong link to illness…
Rabies - rabdovirus.
Zika
Ebola
Covid/SARS
When can non-pathogens create illness in patients?
It can create illness in patients that are immune comprised.
What is a reservoir?
where we find the microbes
What is a vector?
something that transmits the microbe from the reservoir to us
What is a host?
Us – we become this when we are infected – BUT it is more complex than this.
So, why do some organisms almost always make people ill, whilst others only do under certain circumstances, and others only make people who have an underlying defence deficit ill?
A reminder on the Normal Flora (check your I&D notes)
Found on surfaces that are contiguous with the environment
Very complex communities with many species present, mainly bacteria but you do find fungi, parasites and viruses as well
Serve a range of roles that help us – e.g. helping digest food, developing our immune system, blocking sites to prevent pathogens getting a foothold
Importantly – some sites in the body are sterile – so if a member of our own normal flora gets there it can cause severe illness (incl. death)
Where do we get infections from? What order would u rank these as risk factors:
Environmental sources
Food, water, air
Other animals
Directly, indirectly, as food
Other humans
Our own normal flora
Other humans.
Our own normal flora (statistically for women due to UTI).
Food, water, air (microbes cannot replicate in air unless they are in a globule proteinaceous liquid which has been expelled). Air is a vector. Most infections are transmitted in the air between humans. Many bacteria die within five mins of being in air. Many viruses denature.
Directly, indirectly, as food.
Environmental sources.
Other animals.
This is based on UK stats. Will differ overseas.
How do microbes make us ill?
Literally hundreds of ways! But some key themes underpin most of the infections that we see in the UK
A key point is that much of the damage is caused by the immune system “over-reacting” – but without an immune response an unchecked infection could become very severe.
Development of disease is a process, as series of steps – pathogenesis.
The way this progresses in any given part of the body depends on a lot of variables
Is it a sterile site or one with a resident normal flora?
Does the host have a “deficit” that swings the balance in the favour of the microbe?
Has the host been primed previously against infection – either naturally or via vaccination?
NOTES:
Dental plaque - a biofilm with 30 species
Analogy of seating for microbiome control. End students “blocking” the way particular sites.
Why is the UK vaccination schedule different to the rest of the world?
It focuses on the current disease in the UK.
