Questions for Microbiology (practical)

1. Questions for Microbiology (practical) Dr. Nabil El Aila General Microbiology

2. Biosafety • 1- What are the classification of risk groups? • 2- What are the biosafety levels? Give examples of microorganisms belong to each class? • 3- What is the difference between Fume hoods and laminar flow hoods? • 4- Explain the types of Biological safet y cabinet? Why we use them?

3. Microscopy • 1- Mention the types of Microoscopes? • 2- Discuss the principle and use of each microscope? • 3-What are the components of compound microscope and the function of each?

4. Smear preparation and simple staining • 1- What is the functional group of stain? • 2- What are the types of dyes? • 3- What are the types of staining techniques? • 4- Why it is necessary to heat fix bacterial smears? • 5- What would be the reason(s) for not finding any organisms on the slide?

5. Questions on Gram stain • 1-What is the difference in the structure of the cell wall of Gram • positive and Gram negative bacteria with drawing? • 2- Discuss how cell wall structure determines the gram stain • reaction of a bacterium? • 3- What are the conditions when Gram positive bacteria can • appear Gram negative? • 4- Which are bacteria or bacteria component that cant be stained • by Gram stain? • 5- What are the positive and negative control of Gram stain? • 6- Which is the most important step in Gram stain?

6. Questions on Gram stain • 7- Why gram staining is classified as differential staining? • 8- Why are direct gram stains ordered on clinical specimens? • 9- What are the applications of Gram stain? • 10- List all of the things that can go happen during the Gram- • staining process that could lead to an incorrect or poor result? • 11- Why is a gram stain performed on all Cerebrospinal fluid • specimens and not ordinarily done on a) vaginas and b) • stools?

7. Questions on Acid fast stain • 1) Explain the significance of the acid fast stain? • 2) Is a gram stain an adequate substitute for an acid-fast stain? • 3) What are the colors of acid-fast and non acid-fast bacteria like (Escherichia coli and Staph aureus) at the end of the acid-fast stain? Explain in details? • 4) Why is it best to use an old culture for acid fast stain? • 5) What is the purpose of the counterstain in the acid- • fast staining? • 6) Why acid alcohol is used instead of ethyl alcohol in acid fast staining? • 7) What are 2 examples of acid-fast pathogens and what disease they cause?

8. Questions on Special stain • 1) In the Gram stain and the endospore stain, heat fixing is used. • In the capsule stain the cells are not heat fixed. Why? • 2) What is the importance of the capsule stain, the flagella stain • and the endospore stain? • 3) What is the purpose of the Congo red in the capsule stain? • 4) What roles do capsules play in the life of bacteria? • 5) Why don't capsules pick up the stain? • 6) How does the negative stain work? • 7) why doesn't a negative stain colorize the cells in a smear? • 8) List any advantages of a negative stain over a simple stain

9. Questions on Special stain • 9) Define the terms: endospore; vegetative form; germinate. • 10) Describe the unusual characteristics of bacterial spore • 11) Why is a bacterial endospore more difficult to stain then a • vegetative cell? • 12) What differences between young and old culture by • endospore stain?

10. Questions on Culture media • 1) What is general purpose of culture media in microbiology? • 2) What are the different types of media? Explain each of these • types and give examples? • 3) How are media made selective? • 4) How are the media sterilized? Which media are not • autoclavable? • 5) How are media solidified? What is the melting and solidifying • point of the agar? • 6) Why is agar preferred over gelatin? • 7) What is biphasic medi? Give example?

11. Questions on Culture media • 8) Name some lactose fermenters and non lactose fermenters? • 9) Why Gram positive bacteria doesn’t grow in MacConkey • agar? • 10) Why are pH buffers added to the growth media for microbes? • 11) In what size container would you sterilize 500ml of medium? • 12) Why do you incubate the plate inverted?

12. Inoculation and transfer techniques of microorganism • 1)When an agar plate is inoculated, why is the loop flamed • between quadrants? • 2) What is a mixed culture? What is a pure culture? • 3) What is a bacterial colony? • 4) Why is it necessary to isolate individual colonies from a • mixture in the clinical lab? • 5) Give two reasons for using aseptic technique. • 6) List the possible sources of contamination that you should be • concerned about while transferring bacteria from one culture to • another. • 7) How should agar plates be incubated? Why? • 8) Where and how should a label be written on an agar plate?

13. Counting Bacteria • 1) What are the methods used in bacterial counting? Expalin • each of them? • 2) What is the difference between pour plate and spread plate • methods in isolating microorganisms? • 3) What is the main advantage of pour-plate method over other • methods of bacterial colony isolation? • 4) When doing a plate count, why do we choose a plate with 30 – • 300 CFU’s?

14. Counting Bacteria • 5) You count 75 CFU’s on a given plate. The colonies on the plate were formed from 1 ml of original bacterial solution that was serially diluted to 1/100,000 of the original amount. How many bacteria are in the original solution? (Show the proper units.)

15. Bacterial Motility • 1) What advantages does the hanging drop slide have over the • motility test medium for determining motility? • 2) What are the categories of bacterial flagellation? • 3) Give examples of motile and non motile bacteria? • 4) What the different between solid and semisolid media? • 5) What advantage might motile bacteria have over non-motile • ones? • 6) What is the role of mordant in flagellar stain?