Which of the following bacteria is known for producing a capsule that helps it avoid the immune system?
- A. Streptococcus pneumoniae
- B. Escherichia coli
- C. Salmonella enterica
- D. Bacillus subtilis
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is known for producing a capsule that helps it evade the immune system. The capsule acts as a protective barrier, making it difficult for the immune system to recognize and attack the bacteria. Streptococcus pneumoniae is a common cause of pneumonia and meningitis.
Explanation for why other choices are incorrect:
B: Escherichia coli does not typically produce a capsule for immune evasion. It is more commonly associated with gastrointestinal infections.
C: Salmonella enterica also does not produce a capsule for immune evasion. It is known for causing foodborne illness.
D: Bacillus subtilis is a soil bacterium that is not known for producing a capsule to avoid the immune system.
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Which of the following diseases is transmitted via aerosols?
- A. Psittacosis
- B. Shigellosis
- C. Leptospirosis
- D. Giardiasis
Correct Answer: A
Rationale: The correct answer is A: Psittacosis. This disease is transmitted via aerosols containing dried bird droppings or respiratory secretions from infected birds. When these aerosols are inhaled, the bacteria causing psittacosis enter the respiratory system and infect the individual.
- B: Shigellosis is transmitted through contaminated food or water, not via aerosols.
- C: Leptospirosis is transmitted through contact with water, soil, or food contaminated with the urine of infected animals, not via aerosols.
- D: Giardiasis is transmitted through ingesting contaminated food or water, not via aerosols.
Therefore, Psittacosis is the only disease in the list that is transmitted via aerosols, making it the correct answer.
The following spore-forming bacteria can be preserved in soil over a long period of time: clostridia of tetanus, botulism, anaerobic gas infection. Name the way with which these microorganisms get into soil.
- A. With feces
- B. With urine
- C. With water
- D. With industrial waters
Correct Answer: A
Rationale: Step 1: Clostridia of tetanus, botulism, anaerobic gas infection are spore-forming bacteria.
Step 2: Spores are resistant structures that allow bacteria to survive in harsh conditions.
Step 3: Feces contain these spore-forming bacteria due to contamination.
Step 4: When feces are deposited on soil, the spores of these bacteria enter the soil.
Step 5: Spores can remain dormant in soil for long periods.
Summary: Choice A is correct as spore-forming bacteria enter soil through feces, which act as a source of contamination. Choices B, C, and D are incorrect as they do not involve the direct introduction of spores into soil like feces do.
During the staining of sputum smear of a patient with suspected croupous pneumonia the following reactives and stainers were used: gentian violet solution, Lugol's solution, 960 spiritus and water fuchsin. What method of staining is used in this case?
- A. Leffler's
- B. Gram's
- C. Ziehl-Neelsen's
- D. Neisser's
Correct Answer: B
Rationale: The correct answer is B: Gram's staining method. The rationale for this is as follows: Gentian violet and Lugol's solution are used as primary and mordant stains in the Gram's staining method. Spiritus 960 is used as a decolorizer, and water fuchsin is used as a counterstain. This staining method is commonly used in microbiology to differentiate bacteria into Gram-positive and Gram-negative based on their cell wall characteristics.
A: Leffler's staining method is used for the identification of diphtheria bacilli.
C: Ziehl-Neelsen's staining method is used for acid-fast bacteria like Mycobacterium tuberculosis.
D: Neisser's staining method is used for the identification of Neisseria species.
In summary, the use of specific reactives and stainers in the question indicates the application of the Gram's staining method for bacterial differentiation.
Which of the following bacteria is responsible for causing syphilis?
- A. Treponema pallidum
- B. Neisseria gonorrhoeae
- C. Chlamydia trachomatis
- D. Escherichia coli
Correct Answer: A
Rationale: Step 1: Treponema pallidum is a spirochete bacterium known to cause syphilis.
Step 2: It is sexually transmitted and can cause various stages of disease.
Step 3: Neisseria gonorrhoeae causes gonorrhea, not syphilis.
Step 4: Chlamydia trachomatis causes chlamydia, not syphilis.
Step 5: Escherichia coli is a common gut bacterium and not responsible for syphilis. Treponema pallidum is the correct answer as it is the specific bacterium known to cause syphilis.
What is the function of bacterial ribosomes?
- A. DNA replication
- B. Protein synthesis
- C. Energy production
- D. Cell division
Correct Answer: B
Rationale: The correct answer is B: Protein synthesis. Bacterial ribosomes are responsible for translating the genetic information from mRNA into proteins. This process involves the binding of transfer RNA molecules carrying amino acids to the ribosome and the formation of peptide bonds between the amino acids to create proteins. DNA replication (A) is carried out by DNA polymerase enzymes, not ribosomes. Energy production (C) is primarily the function of mitochondria in eukaryotic cells, and cell division (D) is regulated by a complex network of proteins and signaling pathways, not ribosomes.