Microbiology A Systems Approach Test Bank

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A bacteriological laboratory has been investigating a sample of homemade dried fish that was the cause of severe food poisoning. Microscopy of the culture inoculated in Kitt-Tarozzi medium revealed microorganisms resembling a tennis racket. What diagnosis can be made?

  • A. Botulism
  • B. Salmonellosis
  • C. Cholera
  • D. Dysentery
Correct Answer: A

Rationale: The correct answer is A: Botulism. The tennis racket appearance seen under the microscope is characteristic of Clostridium botulinum, the bacterium responsible for botulism. This bacterium produces spores that resemble a tennis racket shape. Botulism is a type of food poisoning caused by the ingestion of the toxin produced by Clostridium botulinum.

Summary:
B: Salmonellosis is caused by Salmonella bacteria, which do not exhibit a tennis racket appearance.
C: Cholera is caused by Vibrio cholerae, which also does not resemble a tennis racket under the microscope.
D: Dysentery is typically caused by bacteria such as Shigella or Entamoeba histolytica, neither of which exhibit the characteristic tennis racket appearance.

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Diaper rash in infants is commonly caused by:

  • A. Sporothrix schenckii
  • B. Actinomyces
  • C. Candida albicans
  • D. Malassezia furfur
Correct Answer: C

Rationale: The correct answer is C: Candida albicans. Candida albicans is a common fungal organism that causes diaper rash in infants due to its ability to thrive in warm, moist environments. It can overgrow in the diaper area, leading to irritation and inflammation. Sporothrix schenckii (A) is a fungus that causes skin infections, but not typically diaper rash. Actinomyces (B) is a bacterium that is not commonly associated with diaper rash. Malassezia furfur (D) is a yeast that causes conditions like dandruff and seborrheic dermatitis, but not diaper rash in infants.

Which of the following bacteria is known for causing the disease known as leprosy?

  • A. Mycobacterium leprae
  • B. Clostridium perfringens
  • C. Streptococcus pneumoniae
  • D. Neisseria gonorrhoeae
Correct Answer: A

Rationale: Step-by-step rationale:
1. Mycobacterium leprae is the correct answer as it is the bacteria known to cause leprosy.
2. Clostridium perfringens is incorrect as it is associated with gas gangrene.
3. Streptococcus pneumoniae is incorrect as it is commonly linked to pneumonia and meningitis.
4. Neisseria gonorrhoeae is incorrect as it causes gonorrhea, a sexually transmitted infection.

In summary, Mycobacterium leprae is the only bacteria among the choices specifically known to cause leprosy, making it the correct answer.

Which of the following consists of DNA viruses?

  • A. Parvoviridae
  • B. Picornaviridae
  • C. Astroviridae
  • D. Togaviridae
Correct Answer: A

Rationale: The correct answer is A: Parvoviridae. Parvoviruses are DNA viruses, as their genetic material is composed of DNA. This distinguishes them from RNA viruses like Picornaviridae, Astroviridae, and Togaviridae. Parvoviruses replicate in the host cell nucleus, further confirming their DNA nature. Therefore, based on their DNA composition and replication process, Parvoviridae is the correct choice.

A 49-year-old countryman got an itching papule on the dorsum of his right hand. In the centre there is a vesicle with serosanginous exudate. Within the next 2 days the patient developed a painless edema of hand and forearm. On the 4th day the temperature rose to 38,5oC, in the right axillary region a large painful lymph node was found. One daybefore the onset of the disease the patient had examined a dead calf. What is the most likely diagnosis?

  • A. Cutaneous anthrax
  • B. Bubonic plague
  • C. Carbuncle
  • D. Lymphocutaneous tularemia
Correct Answer: D

Rationale: The most likely diagnosis is D: Lymphocutaneous tularemia. The key clues include exposure to a dead animal, vesicle with serosanginous exudate, painless edema progressing to lymph node involvement, and fever. Tularemia is caused by Francisella tularensis, commonly acquired through contact with infected animals. The characteristic ulcer at the site of entry, lymphadenopathy, and systemic symptoms point towards tularemia. Cutaneous anthrax (A) presents with a painless ulcer and black eschar. Bubonic plague (B) typically presents with buboes (swollen lymph nodes) and fever. Carbuncle (C) is a deep skin infection typically caused by Staphylococcus aureus.

The role of pili in bacteria is:

  • A. protection from desiccation
  • B. motility
  • C. adhesion to surfaces and conjugation
  • D. spore formation
Correct Answer: C

Rationale: The correct answer is C: adhesion to surfaces and conjugation. Pili are hair-like structures on the surface of bacteria that help them adhere to surfaces and facilitate the transfer of genetic material during conjugation. This is essential for bacterial survival and reproduction. Choice A is incorrect because protection from desiccation is typically associated with other structures like capsules. Choice B is incorrect as motility in bacteria is usually facilitated by flagella. Choice D is incorrect as spore formation involves the formation of specialized structures, not pili.

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