Download 7.3 Search for microbes – Further questions and answers Q1. Bk

7.3 Search for microbes – Further questions and answers
Q1.
Bk Ch7 S7.3 FQ1
a
b
c
Find out what is meant by a ‘notifiable disease’.
Name the notifiable diseases listed under the Health Act in Australia.
Do some library or Internet research to find how hospitals manage these diseases.
A1.
Bk Ch7 S7.3 FA1
a
b
c
Notifiable diseases are infectious diseases that must be reported to the appropriate government if
they have been detected in humans, because there is a potential risk to the community at large.
There is a long list of notifiable diseases in Australia, and these may also vary from state to state.
The list is reviewed regularly. Some examples of notifiable diseases are HIV, hepatitis B,
hepatitis C, typhoid, cholera, Ross River fever, malaria and syphilis.
The management of patients suffering from a notifiable disease depends on the kind of pathogen
involved. For example, if the disease is easily transmitted from one person to another it is
important that the patient is isolated to protect others from infection. Some notifiable diseases are
serious because they have serious health implications for the patient but are not very contagious in
normal circumstances; however, their transmission may be related to lifestyle. In such
circumstances isolation is not necessary but individuals who may be at risk due to their
interactions with the patient may need to be notified.
Q2.
Bk Ch7 S7.3 FQ2
a
b
c
d
What is meant by the term ‘pasteurisation’?
How did the term come about?
Read the information provided on milk cartons or bottles in your home. How is milk treated
before you buy it?
Why is milk pasteurised?
A2.
Bk Ch7 S7.3 FA2
a
b
c
d
Pasteurisation refers to the process of heating foods to a temperature of about 55°C and
maintaining this temperature for a brief period to kill micro-organisms.
Louis Pasteur experimented with micro-organisms and heat and discovered that this process killed
micro-organisms in foods. Hence the term pasteurisation.
Milk is typically pasteurised and homogenised before it arrives on the shop shelves for us to buy.
Pasteurisation is important because it kills micro-organisms that exist in milk that either cause the
milk to spoil quickly or that can cause disease.
Q3.
Bk Ch7 S7.3 Q3
Why is it important to ensure instruments used in surgery and dentistry are sterilised?
A3.
Bk Ch7 S7.3 A3
Instruments used in surgery and dentistry are used again and again between patients. Sterilisation is
important to kill any disease-causing micro-organisms that might otherwise be transmitted from an
infected patient to an uninfected patient via contaminated instruments, for example HIV, hepatitis B,
hepatitis C.
Q4.
Bk Ch7 S7.3 Q4
Choose an example from the work of either Louis Pasteur or Robert Koch to describe how the causal
agent of an infectious disease was identified.
A4.
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© Pearson Australia (a division of Pearson Australia Group Pty Ltd)
Bk Ch7 S7.3 A4
Robert Koch established that micro-organisms were the causal agent for the disease anthrax. He
examined the blood of animals suffering from the disease and discovered that it contained rod-shaped
cells that were not present in the blood of healthy animals. When the blood of infected animals was
injected into healthy animals they also contracted the disease. To establish that infection was caused by
the micro-organisms and not by some other causal agent in the blood he isolated the rod-shaped cells
from the blood of infected animals and injected only these into healthy animals—again the animals
contracted the disease.
Q5.
Bk Ch7 S7.3 Q5
Outline how Koch’s Postulates can be used to identify an organism that is the cause of an infectious
disease.
A5.
Bk Ch7 S7.3 A5
Koch’s Postulates are used to determine whether or not an organism is the cause of an infectious
disease. Firstly, all hosts showing the disease must show the presence of the micro-organism
concerned. The micro-organism must be able to be isolated from the host, cultured in the laboratory
and then inoculated into a healthy individual who then must be shown to develop the disease. If the
micro-organism is isolated from the second host and can be identified as the same organism then it can
be concluded that the micro-organism is the causal agent of the disease.
Q6.
Bk Ch7 S7.4 FQ6
Undertake a research investigation of one of the following infectious diseases:
tetanus pneumonia anthrax fleas aphids encephalopathy (mad cow disease) measles
distemper Creutzfeldt–Jakob disease crown gall tuberculosis chlamydia giardia amoebic
dysentery ringworm liver fluke mildew potato blight myxomatosis calicivirus tinea
ebola
Include the following points in your research:
a
cause of the disease
b
host
c
mode of transmission
d
symptoms
e
host response
f
treatment
g
prevention
h
control.
 References such as Biology texts, medical encyclopaedias or the Internet may be useful.
 Present your findings as a brochure for public information.
 Share your research findings with your class. Overhead transparencies or a computer-based
presentation such as PowerPoint will be a useful way of presenting information to your class.
A6.
Bk Ch7 S7.4 FA6
Example (tetanus):
a
Tetanus is caused by a bacterium, Clostridium tetani.
b
Humans
c
Tetanus bacteria are present in the soil and enter the body at the site of a cut or open wound.
People working or playing in the garden are susceptible to infection when cut by garden
implements, toys, glass, nails, etc. Farmers and people involved in outdoor sports can also be at
risk.
d
Symptoms of tetanus begin with muscle spasm, typically in the jaw first and then spreading to the
rest of the body; the spasms lead to breathing difficulty. If untreated tetanus leads to impairment
of other body functions and is potentially fatal.
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© Pearson Australia (a division of Pearson Australia Group Pty Ltd)
e
f
g
h
Tetanus results in an immune response by the body. This means that the body will mount an
attack on the invading bacteria and produce antibodies against them. If the patient recovers, the
body will keep a memory of the tetanus bacteria and the next time an infection occurs the
invading micro-organisms are destroyed before they have a chance to produce any symptoms.
Unfortunately, tetanus is a serious and vigorous bacterial infection and if untreated can result in
death before the sufferer’s immune system can overcome it.
Tetanus is treated with antibiotics that kill the bacteria. Cuts and abrasions sustained in suspect
conditions should be thoroughly washed with soap and water and followed up immediately with a
medical check. This often includes an inoculation.
Tetanus is easily prevented by regular immunisation.
In Australia tetanus is controlled by the regular immunisation of all infants and children. Boosters
are advisable every 5–10 years.
Q7.
Bk Ch7 S7.4 FQ7
Find out how Howard Florey and Alexander Fleming came upon the discovery of penicillin.
A7.
Bk Ch7 S7.4 FA7
Alexander Fleming came upon the antibiotic effects of the Penicillium mould by accident. He left an
open petri dish infected with Staphylococcus bacteria on the bench of his laboratory near an open
window, forgetting about it when he went away on holiday. During his absence airborne spores of
Penicillium notatum landed on the petri dish and began to germinate and grow. When Fleming returned
he was puzzled at the inhibited growth of the staphylococci. He later showed that it was a substance
produced by the mould that was responsible for the lack of bacterial growth. Howard Florey, along
with two other scientists, was able to extract the antibiotic substance from Penicillium mould and
successfully produced a therapeutic substance that could be used to combat a bacterial infection. In
their first successful attempt they injected lethal doses of Streptococcus bacteria into six mice, then
inoculated four of them with the antibiotic—the four inoculated mice survived while the two without
the antibiotic died.
Q4.
Bk Ch7 S7.4 FQ4
In 1997 a four-month-old baby boy in Japan became infected with Staphylococcus aureus, commonly
known as golden staph. This is a serious bacterial infection that can lead to the death of the patient.
None of the conventional antibiotics used to combat the disease were successful. The boy was
subsequently treated with methicillin and then vancomycin, the strongest available antibiotic. Nothing
worked. The boy eventually recovered when he was treated with experimental antibiotics.
Do some library or Internet research about multi-drug-resistant bacteria. Address the following
questions.
a
What are multi-drug-resistant bacteria?
b
How do bacteria develop resistance to antibiotics?
c
Explain why the strongest antibiotics are not the first ones used to combat serious infections such
as golden staph.
d
Is the way we use antibiotics a factor in the problem of resistance observed in bacteria? Explain.
e
Suggest what the consequences of overusing antibiotics might be in our society. What solutions
can you offer?
A4.
Bk Ch7 S7.4 FA4
a
b
Multi-drug-resistant bacteria are bacteria that have developed a resistance to many of the drugs
(antibiotics) that have traditionally been used to fight them, that is, the antibiotics are ineffective
against these bacteria.
Chance mutations in bacterial DNA can result in resistance to bacteria. However, it is also
understood that some bacteria develop resistance to antibiotics as a response to exposure to the
antibiotic.
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© Pearson Australia (a division of Pearson Australia Group Pty Ltd)
c
d
e
Whenever antibiotics are used there is a chance of resistance occurring in the bacteria that are
exposed to them. If the strongest antibiotic is used first and the bacteria develop a resistance then
there is no more potent antibiotic available to combat the bacteria.
Over-prescription of antibiotics is a factor related to the development of resistance in bacteria.
The more antibiotics are used the greater the chance that a mutant strain of bacteria will be
resistant. When resistant strains appear the usual antibiotics are no longer effective. Failure to
complete a course of antibiotics is also a factor contributing to the development of resistance.
When a course of antibiotics is not completed the patient can have prolonged symptoms or a
relapse, requiring a further course of antibiotics to be prescribed. This serves to prolong the time
of exposure to the antibiotic by bacteria which in turn increases the chance of mutation and
therefore resistance occurring.
Eventually the overuse of antibiotics may lead to a situation in which even the strongest available
antibiotics are ineffective against a particular strain of bacteria. When this happens and
experimental drugs also prove ineffective the patient will die. If such a bacterial strain were to be
transmitted to a number of people we could be faced with an epidemic caused by a ‘superbug’
that we cannot control or overcome. The result of this would be death on a large scale.
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© Pearson Australia (a division of Pearson Australia Group Pty Ltd)