Harmful Microorganisms Revision Pack (B6)

Transcription

1 Disease Transmission: Disease-causing microorganisms can be passed on in a number of different ways; understanding how they are passed on is vital to understanding how to prevent the spread of diseases: Example Microbe How it s spread How it s prevented from spreading Salmonella Spread in food Correct food hygiene (e.g. using different chopping boards for meat) Vibrio Cholera Spread in water Correct water treatment (e.g. not mixing with sewage) Rhinovirus (causes common cold) Spread in airborne droplets Correct use of paper tissues and isolation of patients Other Spread through direct contact Prevented by using barrier methods There are four steps in an infectious disease: STEP 1 The microbe enters the body STEP 2 The incubation period (where the microbe reproduces many times without causing any symptoms in the host STEP 3 The microbe cause the production of toxins STEP 4 The toxins cause the symptoms, e.g. fever There are constantly news stories about disease in areas that have experienced natural disasters; this could be because: Doctors and health professionals collect data on the incidence of different diseases to try and see patterns and make predictions the UK doesn t have many cholera cases because our water is generally quite clean or uncontaminated. Pioneers and treating disease: - Damaged sewage systems may lead to contaminated water - Damage to electricity means fridges stop working, meaning food decays - Large numbers of people moving away to one area means facilities cannot cope - Hospitals may be damaged Many scientists have made IMPORTANT discoveries that have helped to prevent microbes causing diseases three of the most important of these were from Lister, Pasteur and Fleming:

2 Scientist What they did? He discovered that germs cause disease; he realised that microbes from the air could make food go bad. Other doctors and scientists had assumed that it was the disease that caused the bacteria ( spontaneous generation ). Louis Pasteur Joseph Lister Using Pasteur s germ theory, he decided to spray his medical instruments and bandages with carbonic acid this prevented wounds from becoming infected. The death rate among his patients was subsequently cut from 46% to 15%. He is credited with creating the first antiseptic (using the carbonic acid). He noticed in 1928 that some bacteria he had left in a Petri dish had been killed by a naturally occurring fungus called penicillium. This was the first antibiotic, which is known as penicillin. Alexander Fleming Since their respective discoveries, antibiotics and antiseptics have become widely used to control disease: - Antiseptics are used on the outside of the body to kill microbes and prevent their entry into the body - Antibiotics tend to be used inside the body, once the microbes have entered, to kill them - Antiseptics work on MOST microbes, while antibiotics DO NOT work on viruses (which need antiviral medication) Problems are now occurring because many strains of bacteria have become resistant to antibiotics. This resistance is due to a mutation because the bacterium can then survive and reproduce, the resistance is spread by Darwin s process of natural selection. To prevent antibiotic resistance, doctors must take steps: 1) Only prescribe antibiotics when truly necessary 2) Advise that patients finish the dose (use all tablets even if they feel better) so as to kill partially resistant bacteria

3 Past Papers: PPQ(1):

4 PPQ(2): PPQ(3): PPQ(4):

5 PPQ(5): Harmful Microorganisms Revision Pack (B6)

6 PPQ(6): PPQ(7):

7 Mark Schemes: PPQ(1): PPQ(2): PPQ(3): PPQ(4):

8 PPQ(5): PPQ(6): PPQ(7):

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