Harmful Microorganisms

Question 1

Disease-causing microbes can be passed on in a number of different ways.

Answer 1

• Some microbes, such as Salmonella are spread in food. They can be prevented from spreading by correct food hygiene.
• Some, such as Vibrio cholera, may be spread in water. They can be prevented from spreading by correct water treatment.
• Other microbes need direct contact and they can be prevented from spreading by barrier methods.
• Many microbes, such as those that cause influenza, are spread in airbourne droplets. They can be stopped from spreading by correct use of paper tissues and isolation of patients.

Question 2

There are four stages in an infectious diseases:

Answer 2

1. The microbe enters the body.
2. It reproduces many times without causing symptoms. This is the incubation period.
3. The microbes cause the production of many toxins.
4. The toxins cause symptoms, such as fever.

Question 3

We are always hearing about diseases occurring in areas that have experienced natural disasters. This can be for a number of reasons:

Answer 3

• Damage to sewage systems may lead to water supplies being contaminated.
• Damage to electrical supplies may stop refrigerators working, so food decays.
• Large numbers of people moving to other areas means the facilities are not able to cope.
• Hospitals may be damaged, or there may be a shortage of medical staff.

Question 4

Many scientists have made important discoveries that have helped to prevent microbes causing disease. Three the most important of these are:

Answer 4

• Louis Paseur, who helped to prove the germ theory of disease by realising that microbes from the air could make food go bad.
• Joseph Lister, who invented the first antiseptic, using carbolic acid to prevent wounds becoming infected.
• Sir Alexander Fleming, who discovered the first antibiotic, penicillin, which is produced from penicillium, a fungus.

Question 5

How are antispetics and antibiotics used to control disease?

Answer 5

• Antiseptics are used on the outside of the body to kill microbes and prevent their entry.
• Antibiotics tend to be used inside the body to kill microbes once thay have entered.
• Antiseptics work on most microbes but antibiotics have no effect on viruses

Question 6

What problems are occuring now?

Answer 6

Problems are occurring now because some strains of bacteria are developing resistance to antibiotics. This resistance appears in bacterium by mutation. Because the bacteria can then survive and reproduce, the resistance spread by natural selection.

Question 7

To try and prevent antibiotic resistance spreading, doctors take various steps:

Answer 7

• They only prescribe antibiotcs when really necessary.
• They advise patients to always finish the dose so partially resistant bacteria are killed.