chapter 12 p5 Flashcards
Effect on biodiversity:
In the 21st century biodiversity is rapidly being lost around the world, including the destruction of rain forests, the loss of coral reefs and loss of habitat for natural ecosystems in countries all around the world.
This is at least partly due to human activities.
Scientists have not yet explored and identified and analysed a fraction of life on Earth.
One of many reasons why it is so important to maintain biodiversity is to make sure we do not destroy a plant, animal or microorganism which could give us the key to a life-saving drug.
Drug design for the future - Pharmacogenetics:
Personalised medicine
Synthetic biology:
Personalised medicine
- a combination of drugs that work with your individual combination of genetics and disease - is the direction in which medicine is going.
- The human genome can be analysed relatively rapidly and cheaply, giving a growing understanding of the genetic basis of many diseases.
- The science of interweaving knowledge of drug actions with personal genetic material is known as pharmacogenomics.
- We already know that genotypes and drugs interact.
- For example, in approximately 30% of all breast cancers there is a mutation in the HER2 gene.
- The activity of this gene can be shut down by specific drugs - trastuzumab (known an Herceptin) and lapatinib.
- By analsying breast tumours and treating those which have this mutation with the relevant drugs, doctors can reduce the deaths from HER2 breast cancer by up to 50%.
- In future, this type of treatment, where clinicians looks at the genome of their patients and the genome of the invading pathogen before deciding how to treat them, will become increasingly common.
Synthetic biology:
- Using the techniques of genetic engineering, we can develop populations of bacteria to produce much needed drugs that would otherwise be too rare, too expensive or just not available.
- Synthetic biology enables the use of bacteria as biological factories.
- Mammals have also been genetically modified to produce much needed therapeutic proteins in their milk.
- This re-engineering of biological systems for new purposes has great potential in medicine.
- Nanotechnology is another strand of synthetic biology, where tiny, non-natural particles are used for biological purposes - for example, to deliver drugs to very specific sites within the cells of pathogens or tumours.
The antibiotic dilemma:
- At the beginning of the 20’ century, 36% of all deaths - and 52% of all childhood deaths - were from communicable diseases.
- Antibiotics interfere with the metabolism of the bacteria without affecting the metabolism of the human cells - this is called selective toxicity.
- They gave doctors, for the first time, medicines that were effective against bacteria, so antibiotics were understandably, widely used.
- By the start of this century, the numbers of children dying per year had fallen dramatically and, of those remaining few deaths, only about 7% were due to communicable diseases.
- There are many different types of bacteria and a range of antibiotics is used against them, including streptomycin, amoxicillin (very like penicillin), cephalosporins, tetracyclines, sulfonamides, polymixines, ampicillin, and vancomycin.
- In 2014 up to 1 in 6 of all prescriptions were still for antibiotics.
- They are often used for relatively minor infections where the immune system of the patient would deal with the infection with no serious difficulty.
- Unfortunately, antibiotics are becoming less effective in the treatment of bacterial diseases.
- Bacteria are becoming resistant to more and more antibiotics.
- This trend started with penicillin - now there are microorganisms that are resistant to all of the antibiotics we have.
The development of antibiotic resistance
- There is an evolutionary race between scientists and bacteria.
- An antibiotic works because a bacterium has a binding site for the drug, and a metabolic pathway that is affected by the drug.
- If a random mutation during bacterial reproduction produces a bacterium that is not affected by the antibiotic, that is the one which is best fitted to survive and reproduce, passing on the antibiotic resistance mutation to the daughter cells.
- Bacteria reproduce very rapidly, so once a mutation occurs it does not take long to grow a big population of antibiotic-resistant bacteria.
- In a few decades we have reached a stage where increasing numbers of bacterial pathogens are resistant to most or all of our antibiotics.
The development of antibiotic resistancein farming
- In some countries, including the US, farmers routinely add antibiotics to animal feed prophylactically to prevent animals losing condition due to infections, and reducing business profits.
- There are concerns that such routine exposure to the antibiotics accelerates natural selection of antibiotic-resistant strains of both human and animal pathogens.
- However, in the UK it is illegal to give animals routine antibiotics this way.
- Evidence suggests that it is the over subscription of antibiotics to people which is the prime cause of the rise in antibiotic resistance.
antibiotic resistance pathways
MRSA and C. difficile:
Antibiotic-resistant bacteria are a particular problem in hospitals and care homes for older people, where antibiotics are often needed and used.
MRSA (methicillin-resistant Staphylococcus aureus) and Clostridium difficile (C. difficile) have been high-profile examples of antibiotic-resistant bacteria. They are summarised in Table 3.
MRSA
C. difficile:
Antibiotic-resistant infections can be reduced in the long term by measures including:
minimising the use of antibiotics, and ensuring that every course of antibiotics is completed to reduce the risk of resistant individuals surviving and developing into a resistant strain population
good hygiene in hospitals, care homes and in general - this has a major impact on the spread of all infections, including antibiotic-resistant strains.
Solving the problem:
- The development of antibiotic-resistant bacteria is one of the biggest health problems of our time - there is a fear that we may return to the days when bacterial infections killed thousands of people each year in the UK alone.
- Scientists are working on developing new antibiotics using computer modelling and looking at possible sources in a wide variety of places, including soil microorganisms, crocodile blood, fish slime, honey and the deepest abysses of the oceans.
- But at the moment, bacterial resistance is building faster than new antibiotics can be found.
- In 2014 it was announced that a new Lottery-funded prize of £10 million named
Longitude will be reserved for anyone who can come up with a cost-effective, accurate and easy-to-use test for bacterial infections so that doctors all over the world can use the right antibiotics at the right time, and only when they are needed.
