Posted: May 11th, 2015

Immunology and Infectious Diseases IMED2000

1
Immunology and Infectious Diseases IMED2000
Assignment 1 Semester 1 2015
To be submitted electronically on Blackboard via turnitin (details available on
Blackboard), penalties will apply for late submission.
This assignment is worth 15 marks towards your final grade provided you achieve a
satisfactory completion of the practical component of the course.
Question 1-5
View the online lecture on Bacterial Nutrition and Growth. Answer the following questions
related to that lecture. Any additional resources you use should be referenced.
1. Why are high temperatures (far outside the normal range) detrimental to most organisms?
[1 mark]
2. How does the generation time of Mycobacterium tuberculosis influence the characteristics of
tuberculosis as a disease. [1 mark]
3. Why do facultative anaerobes prefer to use oxygen if it is available even though using
oxygen results in toxic waste products? [1 mark]
4. Why are we able to keep honey in the cupboard rather than the refrigerator? In other
words, why don’t we need to worry about bacterial growth in honey? [1 mark]
5. Explain how the growth characteristics of the organism Listeria monocytogenes influence
its’ ability to cause disease? [1 mark]
Question 6-8
To answer these questions you should go to the virtual interactive bacteriology laboratory
website: http://learn.chm.msu.edu/vibl/index.html . Use the menu to navigate to the Differential
Media page and read the material and view the module by clicking on the link. Any additional
resources you use should be referenced.
6. Explain the difference between a selective medium and a differential medium. Give an
example of each type. [2 marks]
7. In the laboratory we plated our nose and throat swabs onto Blood Agar plates which is
an enriched medium. Why did we plate those particular samples on Blood Agar and
not Nutrient Agar? What other useful property does Blood Agar have and what does
it tell us about the bacteria growing on it? [2 marks]
2
8. In laboratory 4 there was a demonstration of the membrane filter technique for determining
the presence of faecal contamination (coliforms) in liquid samples. We used a highly
diluted sample of our E. coli bacteria in our demonstration. The filter was placed on a
MacConkey Agar plate. What colour would we expect the E. coli colonies to be on this plate
and why? [1 mark]
Question 9-10
You may use whatever sources you wish to answer the following questions. Be sure to reference
sources which you do use.
9. A 45 year old male presents to the Emergency Department with a post-operative wound
infection following minor surgery. Swabs are taken from the wound and the laboratory
reports the presence of Staphylococcus aureus (a strict aerobe) and Clostridium septicum (a
strict anaerobe). Explain how it is possible for both organisms to be found in the same
wound when their growth characteristics are fundamentally different. [2 marks]
10. Eating honey can result in botulism, especially in young children. Why would a person be
able to contract botulism, a bacterial disease, if bacteria cannot grow in honey?
[1 mark]
11. In the British Pharmacopeia Category 3A preparations (for oral and rectal administration)
require the absence of Escherichia coli even though this organism is normal flora in the
gastrointestinal tract. Explain why Escherichia coli is required to be absent from these
preparations. [2 marks]
IMPORTANT INFORMATION FOR STUDENTS
Cite the sources of information used for each question in one of the standard formats. The Vancouver system
is preferred. When books are cited it’s necessary to give the page numbers involved. Up to 20% reduction in
marks may occur for lack of referencing, or errors in referencing.
Unless they are given as quotations do not copy exact passages from textbooks as this is plagiarism. You
must paraphrase material by using your own words to demonstrate understanding. Direct copying from
reference sources or other students (past or present) is unacceptable. A zero mark will be awarded where
plagiarism is detected – this includes allowing your work to be copied by others.