Wednesday, July 16, 2008

7 - microbiology basics (mcqs)

1. Name some Gram positive cocci.
- Staphylococcus spp, Streptococcus spp, Micrococcus spp and Enterococcus spp.

2. Name some Gram positive bacilli.
- Clostridium spp, Corynebacterium diphtheriae, Bacillus spp, Listeria sp and Lactobacillus sp.

3. Name some Gram negative bacilli.
- Escherichia coli, Shigella sp, Klebsiella sp, Pseudomonas sp, Vibrio sp and Haemophilus sp.

4. Name some aerobes.
- Mycobacterium tuberculosis, Pseudomonas sp, Micrococcus sp and Acinetobacter sp.

5. Name some obligate anaerobes.
- Clostridium sp, Bacteroides sp and Prevotella sp.

6. Name some facultative anaerobes.
- Staphylococcus aureus and members of Enterobacteriaceae.

7. Name some microaerophilic bacteria.
- Campylobacter sp and Helicobacter sp.

8. Name the capnophilic bacteria.
- Brucella abortus (5 -10% CO2), Pneumococcus, Haemophilus sp and Neisseria sp.

9. Name some motile bacilli.
- Escherichia coli, Vibrio cholerae, Salmonella sp and Proteus sp.

10. Name some non-motile bacilli.
- Klebsiella spp and Shigella spp.

11. Name some capsulated bacteria.
- Klebsiella sp, Pneumococcus, Neisseria meningitidis, Bacillus anthracis, Haemophilus influenzae type b and Vibrio parahaemolyticus.

12. What are the different arrangements of flagella?
- Monotrichous, Lophotrichous, Amphitrichous and Peritrichous.

13. Name some spore bearing bacteria.
- Bacillus spp (aerobic) and Clostridium spp (anaerobic).

14. Name some pigment-producing bacteria.
- Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcens, Chromobacterium violaceum, Prevotella melaninogenica, photochromogens and scotochromogens of Mycobacterium.

15. What is bacterial cell wall made up of?
- Peptidoglycan (mucopeptide).

16. Name bacteria that cannot be stained by Gram’s stain.
- Mycobacterium sp, Chlamydiae, Rickettsiae, Treponema sp, Leptospira sp and Calymmatobacterium granulomatis.

17. Name some bacteria that can not be cultured on artificial culture medium.
- Mycobacterium leprae, Chlamydiae, Rickettsiae, Calymmatobacterium granulomatis and Treponema sp.

18. Name some β–haemolytic bacteria.
- Staphylococcus aureus, Group A & B Streptococcus and Listeria sp.

19. Name some α–haemolytic bacteria.
- Pneumococcus, Viridans Streptococci and some species of Enterococcus.

20. What are “coliforms” and “paracolons”?
- Escherichia coli and Klebsiella sp, which inhabit the intestine are called coliforms. Paracolon is an old term, earlier referred to non-lactose fermenting enteric bacteria other than Salmonella sp, Shigella sp and Proteus sp. They include Enterobacter sp, Citrobacter sp, Hafnia sp etc.

21. What is the normal flora of intestine?
- Bacteroides sp, Escherichia coli, Clostridium sp etc.

22. What is the normal flora of skin?
- Staphylococcus epidermidis, Diphtheroids and Propionibacterium sp.

23. Name some fastidious bacteria.
- Haemophilus sp, Streprococcus sp, Brucella sp, Bordetella sp and Mycobacterium sp.

24. What are Protoplasts, spheroplasts and L-forms?
- Gram positive bacteria without cell wall forms protoplast while gram negative bacteria forms spheroplast. When such forms are able to multiply they are termed L-forms.

25. Name the bacteria that totally lack cell wall.
- Mycoplasma sp and Ureaplasma sp.

26. What is the significance of L–forms?
- They may remain latent in the body, are refractive to antibiotics against cell wall synthesis and causes relapse of infection.

27. How do bacteria multiply?
- Binary fission.

28. What is the nature of bacterial capsule?
- Usually the capsule is made up of polysaccharide, but in Bacillus anthracis the capsule is made up of ployglutamic acid (protein).

Thursday, July 10, 2008

6 - dienes phenomenon

Proteus is a genus of bacteria in the family of Enterobacteriaceae. Proteus species are famous for their swarming on solid culture media.

When different Proteus species swarm towards each other, a line of inhibited growth results where strains meet. This was first observed in 1946 by Dienes and is referred to as the Dienes phenomenon. This line of inhibited growth results from the production of and sensitivity to different types of bacteriocins, namely, proticines, produced by different strains of Proteus species.

If two strains were able to detect different proticines produced by a neighbor, there would be growth inhibition and the formation of a Dienes line. Alternatively, if no proticine difference were detected, the neighboring swarmer would be recognized as "self" and the swarms would interact.

This phenomenon is of value in differentiating the two strains of Proteus for epidemiological purposes.

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