Nokea
A fecal smear from a patient with chronic diarrhea revealed cysts with four nuclei. What is the most likely causative agent?
- A. Entamoeba histolytica
- B. Balantidium coli
- C. Giardia lamblia
- D. Trichomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This protozoan parasite causes amoebic dysentery and is characterized by cysts with four nuclei in fecal smears. It is commonly associated with chronic diarrhea. Balantidium coli (B) presents with large ciliated trophozoites, not cysts. Giardia lamblia (C) has trophozoites with flagella and causes giardiasis, not cysts with four nuclei. Trichomonas hominis (D) typically has a pear-shaped trophozoite and is not associated with cysts with four nuclei.
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Which structure in bacteria allows them to exchange genetic material during conjugation?
- A. Pili
- B. Flagella
- C. Capsule
- D. Ribosomes
Correct Answer: A
Rationale: Pili in bacteria are responsible for conjugation, allowing the transfer of genetic material between cells. They form a bridge between donor and recipient cells, facilitating the exchange of DNA. Flagella are for movement, capsules for protection, and ribosomes for protein synthesis. Pili is the only structure directly involved in genetic material exchange.
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.
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.
Generalization of an intestine infection can be seen in
- A. Salmonella typhi
- B. Shigella flexneri
- C. Helicobacter pylori
- D. None of the above
Correct Answer: A
Rationale: Rationale:
1. Salmonella typhi causes typhoid fever, which can lead to intestinal infections.
2. Shigella flexneri causes dysentery, primarily affecting the colon.
3. Helicobacter pylori causes stomach ulcers, not intestine infections.
Summary:
A is correct as Salmonella typhi causes intestine infection. B and C are incorrect as they cause different gastrointestinal issues. D is incorrect as A is a valid choice.
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.