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.
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The specific prevention (by vaccination) of the disease gas gangrene (caused by Clostridium perfringens) is based on:
- A. Killed whole cell vaccine
- B. Anatoxin
- C. There is no specific prevention by vaccination
- D. Alive attenuated vaccine
Correct Answer: B
Rationale: The correct answer is B: Anatoxin. An anatoxin is a toxin that has been rendered harmless while retaining its ability to stimulate an immune response. Gas gangrene is caused by the toxins produced by Clostridium perfringens, not the bacteria itself. Therefore, vaccination with an anatoxin can trigger the immune system to produce antibodies against the toxin, providing immunity against the disease.
A: Killed whole cell vaccine - Gas gangrene is caused by toxins, not the whole bacterium. This type of vaccine may not be effective in preventing the disease.
C: There is no specific prevention by vaccination - This is incorrect, as vaccination with an anatoxin can prevent gas gangrene.
D: Alive attenuated vaccine - Attenuated vaccines contain live, weakened forms of the pathogen. However, for gas gangrene prevention, targeting the specific toxin with an anatoxin vaccine is more appropriate.
Microscopic analysis of a smear stained by Ziehl-Neelsen method revealed bright red bacilli. What microorganism is being tested for?
- A. Mycobacterium tuberculosis
- B. Staphylococcus aureus
- C. Clostridium tetani
- D. Escherichia coli
Correct Answer: A
Rationale: The Ziehl-Neelsen stain is specific for acid-fast bacteria like Mycobacterium tuberculosis. The bright red bacilli seen in the smear indicate the presence of acid-fast organisms, which is characteristic of Mycobacterium tuberculosis. Staphylococcus aureus, Clostridium tetani, and Escherichia coli are not acid-fast bacteria and would not be stained red using the Ziehl-Neelsen method. Therefore, the correct answer is A: Mycobacterium tuberculosis.
A sputum smear stained by Gram's method revealed Gram-positive cocci in clusters. The patient presented with an abscess. What is the causative agent?
- A. Staphylococcus aureus
- B. Streptococcus pyogenes
- C. Enterococcus faecalis
- D. Micrococcus luteus
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. Staphylococcus aureus is a Gram-positive bacterium that commonly presents as cocci in clusters. It is a known causative agent of abscesses due to its ability to produce enzymes and toxins that contribute to tissue destruction. In this case, the presence of Gram-positive cocci in clusters aligns with the characteristic morphology of Staphylococcus aureus.
Summary of incorrect choices:
B: Streptococcus pyogenes is a Gram-positive bacterium that typically presents as cocci in chains, not clusters. It is more commonly associated with pharyngitis and skin infections rather than abscesses.
C: Enterococcus faecalis is a Gram-positive bacterium that typically presents as cocci in pairs or short chains, not clusters. It is more commonly associated with urinary tract infections and endocarditis.
D: Micrococcus luteus is a Gram-positive bacterium that typically presents as t
Which of the following is a preferred mode of transmission of HIV from a mother to a child
- A. during delivery through mixing of blood
- B. during pregnancy through placenta
- C. via breastmilk during lactation
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because HIV can be transmitted from a mother to a child through multiple modes: during delivery through mixing of blood, during pregnancy through the placenta, and via breastmilk during lactation. Each mode presents a risk of transmission due to the presence of the virus in bodily fluids. Therefore, all of the above options are preferred modes of transmission for HIV from a mother to a child. Choices A, B, and C alone do not fully encompass all the possible routes of transmission, making them incorrect.
The antigen receptors on the surface of B-lymphocytes are made by proteins:
- A. TRUE
- B. FALSE
- C. Both answers can be correct depending on the given situation
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: TRUE. B-lymphocyte antigen receptors are made by proteins called immunoglobulins. These proteins are essential for recognizing and binding to specific antigens. They play a crucial role in the immune response. Choice B is incorrect because B-lymphocyte antigen receptors are indeed made by proteins. Choice C is incorrect as well because in this case, the correct answer is that the receptors are made by proteins. Choice D is also incorrect as the receptors are made by proteins.