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Which organism is responsible for cholera?
- A. Salmonella typhi
- B. Vibrio cholerae
- C. Escherichia coli
- D. Shigella dysenteriae
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by this specific bacterium. Vibrio cholerae produces a toxin that leads to severe diarrhea and dehydration. Salmonella typhi causes typhoid fever, Escherichia coli can cause various infections but not cholera, and Shigella dysenteriae causes dysentery, not cholera. Therefore, the correct choice is B.
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Agglutination reaction is one of the following
- A. Ascoli ring test
- B. Western blot
- C. ELISA
- D. Reaction type Gruber
Correct Answer: A
Rationale: The correct answer is A: Ascoli ring test. Agglutination reaction in the Ascoli ring test is characterized by the formation of a visible ring at the interface of antigen and antibody. This reaction specifically tests for the presence of specific antibodies against antigens in serum, indicating a recent or current infection. The other options, Western blot, ELISA, and Reaction type Gruber, do not involve the agglutination reaction. Western blot and ELISA are immunoassay techniques that detect specific antibodies or antigens, while Reaction type Gruber is not a recognized method in immunology. Therefore, the Ascoli ring test is the correct choice for a test involving agglutination reaction.
Sanitary-biologic examination of air in a drugstore revealed a sanitary-indicative microorganism. Name it:
- A. Staphylococcus aureus
- B. Colon bacillus
- C. Fecal enterococcus
- D. α-haemolytic streptococcus
Correct Answer: C
Rationale: The correct answer is C: Fecal enterococcus. In a drugstore setting, finding a fecal-indicative microorganism like fecal enterococcus indicates a potential contamination from fecal matter, which poses a significant health risk. Staphylococcus aureus (Choice A) and α-haemolytic streptococcus (Choice D) are not typically indicative of fecal contamination. Colon bacillus (Choice B) is a common bacterium found in the gut but is not specifically indicative of fecal contamination. Therefore, choice C, fecal enterococcus, is the most appropriate microorganism indicating unsanitary conditions in a drugstore.
Agents associated with human disease but generally not a serious health risk are classified in which of the following risk groups?
- A. RG1
- B. RG2
- C. RG3
- D. RG4
Correct Answer: B
Rationale: The correct answer is B: RG2. RG2 is appropriate for agents associated with human disease that pose a moderate health risk. These agents may cause disease of varying severity, but generally do not result in serious health consequences. Other choices are incorrect because: A: RG1 is for agents not associated with disease in healthy adults, C: RG3 is for agents associated with serious or lethal human disease, and D: RG4 is for agents that pose a high risk of life-threatening disease and for which there are no treatments.
A patient who has recently come from an endemic area presents with elevated body temperature, headache, chills, malaise, that is with the symptoms which are typical for a common cold. What laboratory tests are necessary to confirm or to refute the diagnosis of malaria?
- A. Microscopy of blood smears
- B. Study of lymph node punctate
- C. Urinalysis
- D. Study of cerebrospinal fluid
Correct Answer: A
Rationale: The correct answer is A: Microscopy of blood smears. Malaria diagnosis is confirmed by identifying the Plasmodium parasite in a blood smear. This step is crucial as it directly visualizes the causative agent. The other choices are incorrect as they do not directly detect malaria parasites. B: Studying lymph node punctate is not specific for malaria. C: Urinalysis does not show malaria parasites. D: Studying cerebrospinal fluid is used to diagnose conditions affecting the brain and spinal cord, not malaria.
Nigrosin is a stain used in:
- A. simple staining
- B. gram staining
- C. negative staining
- D. acid-fast staining
Correct Answer: C
Rationale: Nigrosin is used in negative staining, where the background is stained instead of the cells themselves. This technique helps highlight the morphology and structure of cells that may be damaged by traditional staining methods. Nigrosin is negatively charged and repels the negatively charged bacterial cells, resulting in a clear halo around the cells. This process is particularly useful for observing capsules and determining cell size and shape. The other options are incorrect because simple staining uses a single dye to color the entire cell, gram staining involves a series of dyes to differentiate between gram-positive and gram-negative bacteria, and acid-fast staining is used to detect acid-fast organisms like Mycobacterium.