Answer these questions with a few short sentences, or in dot points. Sometimes d

Question

Answer these questions with a few short sentences, or in dot points. Sometimes diagrams are a good way to answer the question, if so be sure to use labels and explain the diagram. (Generally ,1 mark per fact.)

1. Describe the principles of the capture ELISA test for the direct detection of virus from clinical samples. ?(4 marks)

2. How does Cholera toxin exert its effects? (3 marks) ( or Diptheria toxin, or Botulinum toxin) Use a diagram. What kind of toxins are these?

3. What are the characteristics of  class 2 pathogen? ( or class 1, or class 3)

4. What is the significance of detecting virus- specific IgM in the sera of a patient? (2 marks)

5. What is Otitis media? Describe the pathogenesis, which organisms are common causes? ( 8 marks) could also be an essay question.

6. Why is PCR frequently used for detecting or confirming viral infections? (2 marks)

7. Some bacteria are able to inhibit phagolysosomal fusion. What does this mean and why is this ability considered a virulence factor? (4 marks)

8. What is the difference between a local infection and a systemic infection? (1 marks)

9. What enzyme that assists growth in the urinary tract do all of the following organisms possess? mirabilis,?Ureaplasma urealyticum, S. saprophyticus

10. Explain why it can be difficult to interpret the culture findings from a swab taken from a bedsore? (1 marks)

11. What is an extended spectrum b-lactamase? (4 marks )

12. What is the difference between the minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of an antimicrobial agent? (3 mark)

13. In disc susceptibility testing, what would happen to the zone diameter if the agar was poured too thinly? Explain your answer.

14. What is meant by surrogate testing of an antimicrobial agent? 2 marks

15. Describe the mechanism of action of Penicillin. ( alternative questions mechanism of  fluroquinolones) 6 marks

16. Describe 3 mechanisms of resistance to antimicrobials, and give examples of organisms where this occurs.

17. Tinea pedis:

a). Name a fungus likely to cause tinea pedis in adults in Australia. ?

b). What are the symptoms of this disease? ?

c). What feature is most diagnostic of this fungus? ?

18. Vaginal Thrush:

a). Name the fungus most likely to cause vaginal thrush in Australia. ?

b). What are the symptoms of this disease? ?

c). Describe adiagnostic test for this fungus. ?

19. Pityriasis versicolor

a). Name the fungus that causes pityriasis versicolor in Australia. ?

b). What are the symptoms of this disease? ?

c). Describe the diagnostic feature of this fungus in skin. ?

20. Aspergillosis

a). What are the diagnostic symptoms of aspergillosis? (1 mark) ?

b). Name a site in the body where it is found. ?(1 mark)

c). Is this disease superficial, cutaneous, subcutaneous or systemic? ?(1 mark)

d). What are the diagnostic features of this organism after culture?

Explanation / Answer

Answering any 3 of the questions based on CHEGG rules.

1. If we know which virus are we looking at in clinical sample, first obtain a specific antibody pertaining to any of the important viral protein. One can conjugate the antibody with HRP or use a secondary antibody to detect the virus.

Procedure:

1. Coat the sample with the clinical sample and keep it overnight at 4degC or at 37degC for 2 hours .

2. Block the remaining sites of ELISA plate with 2.5-5 % BSA for 2 hours Room temperature.

3.Add either conjugatd antibody to the plate and incubate at room temperature for 1-2 hours. If primary antibody is not conjugated, still keep the plate at room temperature for 1 hour.

4. Wash the plate with 1X PBST 4-5 times to get rid of excess primary antibodies.

5. If primary antibody is not conjugated, add secondary antibody tagged to HRP and keep it at room temperature for 1 hour.

6. Wash the plate with 1X PBST 5-6 times.

7. Find the absorbance values at 450 nm. If absorbance is seen , then it indicates presence of viral load in the clinical sample.

Question 3. Class 2 pathogens are the ones that has the ability to cause human disease but does not spread so easily to the community. These generally have effective treatments available most of the time.

Class 1 pathogens on the other hand do not cause human disease whereas class 3 pathogens may cause severe human disease and have the tendency to spread to a community., although prophylaxis and effective treatments are available.

Question 4: Most of dengue patients have an elevated levels of IgG M found in their sera.

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