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A patient has a suspected pneumonia. In his sputum there were revealed gram-positive diplococci, prolonged with the slightly pointed opposite ends. What microorganisms are revealed in the sputum?
- A. Staphylococcus aureus
- B. Neisseria gonorrhoeae
- C. Neisseria meningitidis
- D. Streptococcus pneumonia
Correct Answer: A
Rationale: Rationale: The description matches that of Streptococcus pneumoniae, which appears as gram-positive diplococci with slightly pointed opposite ends. Staphylococcus aureus, Neisseria gonorrhoeae, and Neisseria meningitidis do not match the specific characteristics described in the question. Staphylococcus aureus appears in grape-like clusters, while Neisseria species are typically seen as diplococci but lack the pointed shape described. Therefore, the correct answer is A: Staphylococcus aureus.
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By precipitation of tuberculin, a purified protein derivative (PPD) is obtained. It is used in:
- A. Mantoux test
- B. Schick test
- C. Dick test
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Mantoux test. The Mantoux test is used to screen for tuberculosis by injecting PPD intradermally. The presence of a delayed hypersensitivity reaction indicates prior exposure to Mycobacterium tuberculosis. The Schick test (B) is used to test for immunity to diphtheria, while the Dick test (C) is used to test for immunity to scarlet fever. Therefore, the correct use of PPD is in the Mantoux test for tuberculosis screening.
Production of RNA from DNA is called
- A. Transposition
- B. Translation
- C. Transcription
- D. RNA splicing
Correct Answer: C
Rationale: The correct answer is C: Transcription. Transcription is the process of synthesizing RNA from a DNA template. During transcription, RNA polymerase binds to the DNA and produces a complementary RNA strand. This process is essential for gene expression.
Explanation for why other choices are incorrect:
A: Transposition involves the movement of genetic elements within a genome, not the production of RNA from DNA.
B: Translation is the process of synthesizing proteins from mRNA, not the production of RNA from DNA.
D: RNA splicing is the process of removing introns and joining exons in pre-mRNA to produce mature mRNA, not the initial production of RNA from DNA.
Which of the following bacteria causes the disease diphtheria?
- A. Bordetella pertussis
- B. Corynebacterium diphtheriae
- C. Streptococcus pyogenes
- D. Neisseria meningitidis
Correct Answer: B
Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria by inhibiting protein synthesis, leading to the formation of a pseudomembrane in the throat. Bordetella pertussis causes whooping cough, Streptococcus pyogenes causes strep throat, and Neisseria meningitidis causes meningitis. Corynebacterium diphtheriae is the only bacterium among the choices known to cause diphtheria due to its specific toxin production.
While examining the feces of a patient with diarrhea, cysts with four nuclei were found. What protozoan is most likely causing the condition?
- A. Entamoeba histolytica
- B. Lamblia
- C. Trichomonas
- D. Balantidium
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This protozoan causes amoebiasis, which presents with symptoms like diarrhea. The cysts with four nuclei found in the feces are characteristic of Entamoeba histolytica. This protozoan is known to cause invasive infection, leading to tissue destruction and ulcers in the intestines. Lamblia (choice B) typically presents with cysts containing two nuclei. Trichomonas (choice C) is a sexually transmitted parasite and does not form cysts. Balantidium (choice D) is a ciliated protozoan that does not have four nuclei in its cyst form.
Bacteria causing bacillary dysentery can be isolated from the patient's blood:
- A. There is no bacteremia
- B. During the second week of illness
- C. During the first week of illness
- D. None of the above
Correct Answer: A
Rationale: Rationale:
1. Bacillary dysentery primarily affects the intestinal tract, not the bloodstream.
2. Bacteremia is rare in bacillary dysentery, as the infection is localized.
3. Isolating bacteria from the blood is not a typical diagnostic feature.
4. Therefore, the correct answer is A.
Summary:
Bacteria causing bacillary dysentery are not typically isolated from the patient's blood due to the localized nature of the infection. Choices B and C are incorrect as they suggest specific timeframes, which are not relevant to bacteremia in this context. Choice D is incorrect as bacteremia is not associated with bacillary dysentery.