Nokea
For infections caused by coronaviruses is NOT true that;
- A. Most commonly associated with URT infections
- B. May be asymptomatic
- C. SARS is an atypical pneumonia that can be complicated with acute respiratory failure and can cause death
- D. Reinfections cannot be observed
Correct Answer: D
Rationale: Step-by-step rationale for why answer choice D is correct:
1. Coronaviruses can cause reinfections due to potential waning immunity.
2. Studies have shown cases of reinfections with different strains or within a short period.
3. This contradicts the notion that reinfections cannot be observed.
Summary:
A: Incorrect because some coronaviruses can cause lower respiratory tract infections.
B: Incorrect as coronaviruses can exhibit varied symptomatology including asymptomatic cases.
C: Incorrect as some coronaviruses like SARS can lead to severe pneumonia and complications.
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Francisella tularensis is a:
- A. spore forming encapsulated gram-negative bacterium
- B. non-spore forming encapsulated gram-negative bacterium
- C. non-spore forming non-capsulated gram-negative bacterium
- D. spore forming non-capsulated gram-negative bacterium
Correct Answer: B
Rationale: The correct answer is B: non-spore forming encapsulated gram-negative bacterium. Francisella tularensis is a non-spore forming bacterium, which rules out choices A and D. It is encapsulated, which eliminates choice C. The encapsulation of the bacterium helps it evade the host immune system, leading to its pathogenicity. This encapsulated bacterium is responsible for causing the zoonotic disease tularemia in humans.
A lymph node punctate of a patient with suspected protozoa disease was examined. Examination of the stained specimen (Romanovsky's stain) revealed some crescent bodies with pointed end, blue cytoplasm and red nucleus. What protozoan were revealed in the smears?
- A. Toxoplasmas
- B. Malarial plasmodiums
- C. Dermotropic leishmania
- D. Viscerotropic leishmania
Correct Answer: B
Rationale: The correct answer is B: Malarial plasmodiums. The description of crescent bodies with a pointed end, blue cytoplasm, and red nucleus corresponds to the characteristics of Plasmodium species seen in Romanovsky's stain. Plasmodium species are known to cause malaria and have distinct features like the ones described.
Incorrect choices:
A: Toxoplasmas - Toxoplasma gondii typically appear as tachyzoites or bradyzoites under staining, not crescent bodies.
C: Dermotropic leishmania - Leishmania species appear as amastigotes in tissue smears, not crescent bodies.
D: Viscerotropic leishmania - Similar to choice C, Leishmania species do not typically present as crescent bodies in stained specimens.
Which of the following bacteria produce exotoxins that cause severe gastrointestinal illness?
- A. Clostridium botulinum
- B. Vibrio cholerae
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D (All of the above) because all three bacteria listed produce exotoxins that cause severe gastrointestinal illness. Clostridium botulinum produces botulinum toxin causing botulism. Vibrio cholerae produces cholera toxin leading to cholera. Escherichia coli can produce various exotoxins causing different types of severe gastrointestinal illnesses like E. coli O157:H7 causing bloody diarrhea. Therefore, all choices A, B, and C are correct in this case as they all produce exotoxins causing severe gastrointestinal illness.
Which are the epidemic typhus vectors:
- A. Head lice
- B. Body lice
- C. Fleas
- D. Ticks
Correct Answer: A
Rationale: The correct answer is A: Head lice. Epidemic typhus is transmitted by the body louse, Pediculus humanus humanus, which is different from the head louse, Pediculus humanus capitis. Head lice are not known to transmit epidemic typhus. Body lice are the primary vectors for transmitting epidemic typhus. Fleas are vectors for other diseases such as plague, not epidemic typhus. Ticks are vectors for various diseases but not for epidemic typhus. Therefore, the correct vector for epidemic typhus transmission is body lice, making choice A the correct answer.
The most common bacterial species in hospital environment is:
- A. Borrelia burgdorferi
- B. Staphylococcus aureus
- C. Bacillus cereus
- D. Staphylococcus haemolyticus
Correct Answer: B
Rationale: The correct answer is B: Staphylococcus aureus. This bacterium is commonly found in hospital environments due to its ability to colonize human skin and mucous membranes. It is a leading cause of hospital-acquired infections. Borrelia burgdorferi is mainly associated with Lyme disease transmitted by ticks, not commonly found in hospitals. Bacillus cereus is a foodborne pathogen, not typically prevalent in hospital settings. Staphylococcus haemolyticus is a coagulase-negative staphylococcus species, less pathogenic and less common in hospitals compared to Staphylococcus aureus.