microbiology chapter 12 test bank

microbiology chapter 12 test bank Related

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A patient with fever, chills, and neck stiffness had a cerebrospinal fluid sample with Gram-negative diplococci. What is the likely diagnosis?

  • A. Meningococcal meningitis
  • B. Pneumococcal meningitis
  • C. Haemophilus influenzae meningitis
  • D. Listeria monocytogenes meningitis
Correct Answer: A

Rationale: The likely diagnosis is Meningococcal meningitis (Choice A) due to the presence of Gram-negative diplococci in the cerebrospinal fluid. Neisseria meningitidis is a Gram-negative diplococcus commonly associated with meningococcal meningitis. Fever, chills, and neck stiffness are classic symptoms of bacterial meningitis, and Neisseria meningitidis often presents with these symptoms. Pneumococcal meningitis (Choice B) is caused by Streptococcus pneumoniae, a Gram-positive organism. Haemophilus influenzae (Choice C) is also a Gram-negative organism but typically presents with a different clinical picture. Listeria monocytogenes (Choice D) is a Gram-positive rod and is more commonly associated with meningitis in neonates, elderly, and immunocompromised individuals.

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Which toxin is specific for ETEC:

  • A. TSST-1
  • B. Shiga-like toxin
  • C. Erythrogenic toxin
  • D. LT enterotoxin
Correct Answer: D

Rationale: The correct answer is D: LT enterotoxin. This toxin is specific for Enterotoxigenic E. coli (ETEC) and is responsible for causing diarrhea by increasing cyclic AMP levels in intestinal cells. TSST-1 (choice A) is produced by Staphylococcus aureus, not ETEC. Shiga-like toxin (choice B) is produced by Shigella and EHEC, not ETEC. Erythrogenic toxin (choice C) is produced by Streptococcus pyogenes, not ETEC. Therefore, the LT enterotoxin is the specific toxin associated with ETEC.

The generation time of Escherichia coli is

  • A. 20 min
  • B. 60 min
  • C. 20 hours
  • D. 24 hours
Correct Answer: A

Rationale: The correct answer is A (20 min) because Escherichia coli typically has a generation time of around 20 minutes, meaning the time it takes for a bacterial population to double. This rapid reproduction rate is a key characteristic of E. coli. Option B (60 min) is incorrect as it is longer than the usual generation time. Option C (20 hours) is too long for E. coli's generation time. Option D (24 hours) is also incorrect as it is much longer than the typical generation time of E. coli.

The primary stage of syphilis is usually manifested as:

  • A. Diffuse maculopapular rush
  • B. Purulent exudation from the urethra
  • C. Syphilitic granulomas (gummas)
  • D. Non-tender chancre (ulcus durum)
Correct Answer: D

Rationale: The correct answer is D: Non-tender chancre (ulcus durum). In the primary stage of syphilis, an individual typically develops a painless ulcer known as a chancre at the site of infection. This ulcer is usually firm, round, and clean with well-defined borders. It is important to note that it is non-tender, which distinguishes it from other skin conditions. This characteristic helps healthcare providers differentiate syphilis from other sexually transmitted infections.

Explanation for other choices:
A: Diffuse maculopapular rash - This is more commonly associated with secondary syphilis.
B: Purulent exudation from the urethra - This is not a typical presentation of primary syphilis.
C: Syphilitic granulomas (gummas) - Gummas typically develop in the tertiary stage of syphilis, not in the primary stage.

What is the mechanism of action of the exotoxin C. Diphtheriae?

  • A. Inhibits the release of acetylcholine
  • B. Blocks the inhibitory neurotransmitters release
  • C. Inhibits protein synthesis
  • D. None of the above
Correct Answer: C

Rationale: The correct answer is C: Inhibits protein synthesis. Exotoxin of C. Diphtheriae acts by inhibiting protein synthesis in host cells. This disrupts cellular functions and leads to tissue damage. Choice A is incorrect because acetylcholine release is not affected. Choice B is incorrect as it does not involve neurotransmitters. Choice D is incorrect as the exotoxin does have a specific mechanism.

Sanitary and bacteriological examination of air in drug-store premises revealed increased content of sanitary representative microorganisms. What microorganisms are these?

  • A. Golden staphylococcus and hemolytic streptococcus
  • B. Diphtheria and tuberculosis bacilli
  • C. Colon and blue pus bacilli
  • D. Epidermal staphylococcus and sarcina
Correct Answer: A

Rationale: The correct answer is A (Golden staphylococcus and hemolytic streptococcus) because these microorganisms are commonly found in the air of contaminated environments like drug-store premises. Golden staphylococcus and hemolytic streptococcus are pathogenic bacteria associated with infections in humans, indicating poor sanitation. The other choices are incorrect because:
B: Diphtheria and tuberculosis bacilli are not commonly found in the air in drug-store premises.
C: Colon and blue pus bacilli are not typical microorganisms associated with air contamination.
D: Epidermal staphylococcus and sarcina are not likely to be present in high amounts in the air of drug-store premises.

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