From this lecture you should understand
What is antibiotic resistance
How antibiotic resistance emerges
Main mechanisms of antibiotic resistance and suitable examples of each
Difference between adaptive and mutational resistance
What is antibiotic resistance.
• The ability of bacteria t...
Lecture overview.
From this lecture you should understand
What is antibiotic resistance
How antibiotic resistance emerges
Main mechanisms of antibiotic resistance and suitable examples of each
Difference between adaptive and mutational resistance
What is antibiotic resistance.
The ability of bacteria to survive treatment by certain antibiotics.
Bacteria which are resistant to multiple antibiotics are called multi-drug resistant
bacteria
MSRA- well known superbug.
MSRA- methycline resistant staphylococcus aureus.
The bcateria, that are causing our infections, become resistant to antibiotics
Why is the problem of AMR so bad?
Antibiotic use in humans
• People not taking complete courses of antibiotics
• Inappropriate prescriptions or over-prescription of antibiotics
• Over-prescription of antibiotics.
• Delayed prescription is a solution to this
Non-therapeutic uses of antibiotics
• To treat sick animals in vet medicine
• As growth promoters in
agriculture (Not in the EU!). Pump chicken with antibiotics and it grows. When we eat the
chicken we will also be eating residual antibiotics within the chicken.
• Biocide use- present in toothpaste. Triclasan has been shown to perpetuate
antibiotic resistance. Banned in the EU.
• Brewing- we use antibiotics in this because bacteria spoils beers.
• Aquaculture- fish farming
• Anti-fouling (industrial, ships)- stop photosynthetic algae growing and building up.
Stop clogging up boat engines. This goes out into the sea’s, this is where the fish are.
We then catch the fish and ingest them and the antibiotics.
• Antibiotics in the sea, fish eat antibiotics and we eat the fish.
There are no new antibiotics.
The golden age was up to the 70s.
Only 2 new antibiotics discovered and approved for use for humans since the 2000s.
We have no more.
We found the easy antibiotics, all the saphrophytic microorganisms that live in the soil, that
are secreting antibiotics, we found them and we identified those antibiotics and we cultured
, them on scale and we ate them like sweets and as a consequence we have resistance to
every class of antibiotics on that screen.
Novel therapeutics are desperately needed to combat antibiotic resistant infections, there
are patients dying every year because of antibiotic resistant infections.
Antibiotic sensitivity reports mainly show resistance for patients.
Why do antibiotics stop working.
Analogy:
You have a bacterial tonsilitis, you have the bacteria at the sight of infection in you’re
tonsils.
This causes inflammation.
The inflammation is causing pain. Therefore, you have very painful swollen tonsils.
The GP, says you may have bacterial tonsilitis, they may tell you it may be a viral infection
and they will give you a prescription.
You take the prescription antibiotics, the antibiotics kill 90% of bacteria at the site of
infection in the first 24 hours.
After 24/48 hours you start to feel a little bit better, after 72 hours, you’re inflammation has
reduced massively, so you no longer have the pain and the symptoms of infection, but you
still have 10% of bacteria remaining at the site of infection.
These are called persister populations.
If you stop taking the antibiotics when you feel better, these persister populations can
recolonize.
The persister populations are potentially different to the population that was causing your
infection in the first place.
They have something different about them: this could be genetic, metabolically or some sort
of evolutionary change.
This means that they have been able to survive that sub-inhibitory concentration of
antibiotic. So, they grow back.
But you go back to the doctor because you still have a sore throat and the doctor will now
give you different antibiotics because those ones did not work on you and you have become
resistant to them.
Then they do the same thing and this is how antibiotic resistance develops.
Antibiotics.
Persister populations- may lyse eventually but are not lysing right now.
If you remove the antibiotics at this stage, you have killed the bacteria, but the persister
population bacteria are still there and surviving.
So you have selected for a trait in terms of evolutionary selection. These could be resistant
bacteria that are persistent
The evolution of antibiotic resistance.
Demonstrates how quickly and efiiciently bacteria evolve antibiotic resistance
How do bacteria become resistant to antibiotics?
1. Make enzymes which alter or destroy the antibiotic. These enzymes are like
molecular cookie monsters, they get through the antibiotic as fast and efficiently as
the cookie monster gets through cookies.
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