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A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely causative agent?

  • A. Staphylococcus epidermidis
  • B. Staphylococcus aureus
  • C. Streptococcus pyogenes
  • D. Enterococcus faecalis
Correct Answer: A

Rationale: The most likely causative agent in this case is Staphylococcus epidermidis. This conclusion can be drawn based on the characteristics provided: Gram-positive cocci in clusters, catalase-positive, and coagulase-negative. Staphylococcus epidermidis fits all these criteria.

Explanation of other choices:
- Staphylococcus aureus: Typically coagulase-positive, so it does not match the characteristics given.
- Streptococcus pyogenes: Gram-positive cocci in chains, not clusters. Also, it is catalase-negative.
- Enterococcus faecalis: Gram-positive cocci in pairs or chains, not clusters. Additionally, it is catalase-negative.

Therefore, Staphylococcus epidermidis is the most likely causative agent based on the provided characteristics.

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How many types of herpes simplex virus are there?

  • A. 1
  • B. 2
  • C. 3
  • D. 4
Correct Answer: B

Rationale: The correct answer is B because there are two types of herpes simplex virus: HSV-1 and HSV-2. HSV-1 typically causes oral herpes, while HSV-2 usually causes genital herpes. Choice A is incorrect because there is more than one type. Choices C and D are also incorrect as there are only two types of herpes simplex virus known to infect humans.

A patient presented with fever and cough. A sputum sample stained by Gram's method revealed Gram-positive diplococci with a capsule. What is the likely causative agent?

  • A. Streptococcus pneumoniae
  • B. Staphylococcus aureus
  • C. Neisseria meningitidis
  • D. Klebsiella pneumoniae
Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive diplococci with a capsule is characteristic of S. pneumoniae. This bacterium is a common cause of pneumonia, especially in patients with fever and cough. It is also known for causing infections such as otitis media and sinusitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form diplococci or have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus commonly associated with meningitis, not pneumonia. Klebsiella pneumoniae (D) is a Gram-negative rod, not a diplococcus, and is more commonly associated with pneumonia in immunocompromised patients.

A 28 y.o. patient without permanent residence was admitted to the hospital with the preliminary diagnosis influenza. On the fith day of illness he got a maculopapular petechial rash on his body and internal surfaces of extremities. Body temperature is 410 C, euphoria, face hyperemia, sclera reddening, tongue tremor, tachycardia, splenomegaly, excitement. What is the most probable diagnosis?

  • A. Epidemic typhus
  • B. Delirium alcoholicum
  • C. Leptospirosis
  • D. Measles
Correct Answer: A

Rationale: Step 1: Initial diagnosis of influenza suggests a viral illness.
Step 2: Presence of maculopapular petechial rash and high fever indicates a systemic infection.
Step 3: Symptoms like euphoria, hyperemia, tachycardia, splenomegaly, and excitement are characteristic of epidemic typhus.
Step 4: Face hyperemia, sclera reddening, and tongue tremor are specific to epidemic typhus.
Step 5: Epidemic typhus is transmitted by body lice, which fits the scenario of a patient without permanent residence.
Summary:
- Delirium alcoholicum is unlikely due to the specific symptoms and lack of history of alcohol abuse.
- Leptospirosis typically presents with jaundice and renal symptoms, not seen in this case.
- Measles rash is different from the maculopapular petechial rash described.

Bacteria that thrive in high salt concentrations are called:

  • A. acidophiles
  • B. thermophiles
  • C. halophiles
  • D. mesophiles
Correct Answer: C

Rationale: The correct answer is C: halophiles. Halophiles are bacteria that thrive in high salt concentrations due to their ability to regulate osmotic pressure. They have adapted mechanisms to survive in such extreme environments. Option A, acidophiles, thrive in acidic conditions, not high salt concentrations. Option B, thermophiles, thrive in high temperature environments. Option D, mesophiles, thrive in moderate temperature conditions, not necessarily high salt concentrations. Therefore, the correct choice is C as it specifically refers to bacteria that thrive in high salt concentrations.

Infectious mononucleosis most often occurs in:

  • A. infants
  • B. adolescents
  • C. young adults
  • D. the elderly
Correct Answer: B

Rationale: The correct answer is B: adolescents. Infectious mononucleosis is commonly caused by the Epstein-Barr virus, which is transmitted through saliva. Adolescents are more likely to engage in activities like kissing and sharing drinks, increasing the chances of virus transmission. Infants have maternal antibodies for protection, young adults may have developed immunity, and the elderly have had more exposure to the virus and may have built immunity over time.

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