Sample/practice exam 2014, questions - study questions for medical microbiology PDF

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study questions for medical microbiology...

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The Clinical Microbiology Laboratory 1-Mark questions 1. What part of a microbiology specimen report (lab result) do most doctors place a high degree of significance to? 2. In what situations would an accurate species identification be important? List two reasons. 3. What is the relationship between specimen quality and the time interval between collection and processing? 4. What is the ideal maximum elapsed time between collection and processing? 5. What are two advantages of placing a swab in transport media? 6. List two specimens that have a high priority once in the lab? 7. What is the significance of seeing PMN cells in a wet preparation or stained smear? 8. What does the presence of large numbers of epithelial cells in either a sputum or urine sample indicate? 9. Why are CHOC plates always incubated in CO2?

4-mark Questions – may require detailed explanations for full marks to be awarded 1. Explain why MacConkey agar (MAC) is considered to be selective and differential (i.e. how does it work)? 2. Explain why Mannitol Salt agar (MSA) is selective and differential (i.e. explain how it works)? 3. List 4 guidelines for ensuring a good quality specimen. 4. List 4 reasons why a laboratory might reject a specimen?

Systematics 1-Mark Questions 1. Which discipline of taxonomy is responsible for giving an organism a scientific name? 2. What is an obligate aerobe? 3. Give an example of an obligate aerobe (genus and species)? 4. What is an obligate anaerobe? 5. Give an example of an obligate anaerobe (genus and species)? 6. What is a facultative organism? 7. Give an example of a facultative organism (genus and species)? 8. What does microaerophilic mean? 9. Name a genus of bacteria that has this characteristic (Q9)? 10. What is a capnophile? 11. Name a genus of bacteria that has this characteristic (Q10)? 12. List the genus and species of an organism that is acid fast. 13. Which genera of bacteria produce spores? 14. Why do you have to be careful when performing a catalase test on a colony taken from BA? 15. What precautions do you need to take when performing an oxidase test?

4-Mark Questions – high detail expected for full marks 1. Explain the principle of the Gram stain (how and why it works), including the colour of both Gneg and Gpos cells at the completion of each staining step. 2. Explain the principle of action of the catalase test? (how does it work, what is happening?)

3. Explain how to interpret the OF test. 4. In phenotypic tables for bacteria, what does a “+”, “-” and “d” represent?

Gram Positive Cocci (1) 1-Mark Questions 1. What two primary test results (systematics) would indicate that you should consider an isolate as belonging to the genus Staphylococcus? 2. What is the difference between plasma and serum? 3. What type of infection is S.saprophyticus normally associated with? (1/2 mark) Is it Novobiocin resistant or susceptible? (1/2 mark) 4. List two virulence factors for S .epidermidis? 5. What does MRSA stand for?

4-Mark Questions 6. List the 4 virulence factors of S.aureus and give one example of why or how each one acts to assist in the ability of the organism to cause infection? 7. What test divides all staphylococci into two groups? (1 mark) Explain the theory behind the rapid version of this test, i.e. how it works NOT how to do it? 8. What factors would help to determine the clinical significance of isolating a coagulase negative staphylococci (CoNS)? 9. What type of infections is S.epidermidis normally associated with and why?

Gram Positive Cocci (2) 1-Mark Questions 1. What is the scientific name for Group A Streptococcus? 2. What is the scientific name for Group B Streptococcus? 3. What antibiotic is the drug of choice used to treat suspected streptococcal pharyngitis? 4. If you identified an unknown organism as a GPC that was catalase negative and was hippurate positive, what would the likely identity be? 5. If you identified a GPC that was catalase negative and was sensitive to Bacitracin what would the most likely identity be? 6. How could you easily differentiate between S.pneumoniae and a member of the viridans streptococci? 7. Which is the most commonly isolated species of enterococci? 8. Where is group B strep. MOST likely to be found as NF? 9. What is the principle difference in the colony morphologies between Gp A & Gp B strep? 10. What systemic infection are the viridans streptococci usually associated with? 11. What is the advantage of using the bile solubility test over the optochin test when using these to ID S.pneumoniae?

4-Mark Questions 12. What are the main identifying features of S.pneumoniae? (1° + 2° features/test results) 13. What immunological property is thought to play an important role in conferring protection against pneumococcal infection? What 3 groups of people would most likely be affected? 14. List four virulence factors of Group A Streptococcus and give an example of how or why each acts to confer pathogenicity?

15. Differentiate/compare between post streptococcal rheumatic fever and glomerular nephritis. 16. Why do you think that organisms of the genus Enterococcus are frequently associated with significant nosocomial infections? (2 reasons, explain each)

Gram Negative Bacteria 1-Mark Questions 1. List two properties/characteristics of Gram negative endotoxins? 2. Which genera from the family enterobacteriaceae are always non-motile? 3. What genera of enterobacteriaceae would you expect to isolate if an unknown organism was TDA positive? 4. How would you know if an unknown organism was a member of the enterobacteria/ceae family and not a member of the genera Pseudomonas, Vibrio or Aeromonas? (hint: rapid test) 5. Where is Pseudomonas aeruginosa normally found? 6. What does zoonoses mean? 7. Where are O and H antigens located? 8. How could you tell if an organism growing on a culture plate is encapsulated? 9. Where are members of the genera Haemophilus, Neisseria and Moraxella found as normal flora? 10. What type of infections are Haemophilus and Moraxella usually associated with?

4-Mark Questions 1. What primary test results would you expect for a member of the enterobacteriaceae?

2. How could you differentiate between two swarming strains of Proteus? What would be the results for each? 3. If you had a mucoid LF/LLF growing on CLED or MAC, how could you differentiate this as either an Enterobacter sp. or a Klebsiella sp. without setting up overnight tests? 4. List 4 laboratory features of Pseudomonas aeruginosa....