Nokea
Gram staining is used to differentiate bacteria based on:
- A. size and shape
- B. presence of flagella
- C. cell wall composition
- D. genetic material
Correct Answer: C
Rationale: The correct answer is C: cell wall composition. Gram staining differentiates bacteria based on the structure of their cell walls. It classifies bacteria into Gram-positive (thick peptidoglycan layer) and Gram-negative (thin peptidoglycan layer). This differentiation is crucial for identifying bacterial species and guiding treatment choices. Size and shape (choice A) are not specific to Gram staining. Presence of flagella (choice B) is related to bacterial motility, not Gram staining. Genetic material (choice D) is not directly assessed by Gram staining. Overall, the unique composition of the cell wall is the key factor in distinguishing bacteria through Gram staining.
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Which bacteria is commonly associated with foodborne illnesses caused by contaminated water?
- A. Vibrio cholerae
- B. Clostridium difficile
- C. Mycobacterium tuberculosis
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae. This bacterium is commonly associated with foodborne illnesses caused by contaminated water due to its ability to survive and multiply in water sources. Vibrio cholerae causes cholera, a severe gastrointestinal infection transmitted through contaminated food and water. Clostridium difficile, Mycobacterium tuberculosis, and Neisseria gonorrhoeae are not typically associated with foodborne illnesses caused by contaminated water. Clostridium difficile causes gastrointestinal infections linked to antibiotic use, Mycobacterium tuberculosis causes tuberculosis through respiratory transmission, and Neisseria gonorrhoeae causes sexually transmitted infections.
A smear of streptobacillus preparation stained by Ozheshko method has been studied microscopically with oil immersion. What structural feature of the bacteria has been studied?
- A. Spores
- B. Capsule
- C. Flagella
- D. Inclusions
Correct Answer: A
Rationale: The correct answer is A: Spores. The Ozheshko method is used to stain spores, which are resistant structures produced by certain bacterial species. By studying the smear of streptobacillus preparation under oil immersion, one can observe the presence of spores as distinct, oval bodies within the bacteria. Spores are important for bacterial survival in harsh conditions.
Summary:
B: Capsules are not typically stained using the Ozheshko method. Capsules are usually visualized using negative staining techniques.
C: Flagella are not stained by the Ozheshko method. Flagella are visualized using special staining techniques like the flagella stain.
D: Inclusions are not specifically stained by the Ozheshko method. Inclusions are often observed using techniques that highlight cellular structures or components.
Which of the following bacteria produces a neurotoxin that causes botulism?
- A. Clostridium botulinum
- B. Clostridium tetani
- C. Escherichia coli
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum. Clostridium botulinum produces the neurotoxin that causes botulism. This bacterium thrives in anaerobic conditions and contaminated food. The neurotoxin blocks acetylcholine release at the neuromuscular junction, leading to muscle paralysis. Choices B, C, and D are incorrect because Clostridium tetani causes tetanus, Escherichia coli can cause food poisoning but not botulism, and Staphylococcus aureus produces enterotoxins causing food poisoning, not botulism.
In a village, a case of anthrax had been registered. Medical services began epidemiologically indicated specific prophylaxis of population against anthrax. What preparation was used for this purpose?
- A. Anatoxin
- B. Inactivated vaccine
- C. Chemical vaccine
- D. Genetically engineered vaccine
Correct Answer: A
Rationale: The correct answer is A: Anatoxin. An anatoxin is a preparation that contains inactivated toxins produced by the anthrax-causing bacteria. By administering anatoxin, the population can develop immunity against the toxin without being exposed to the live bacteria. This specific prophylaxis approach helps prevent the development of anthrax infection by targeting the toxin itself.
Summary:
- Choice B (Inactivated vaccine) is incorrect because an inactivated vaccine typically contains killed or inactivated whole bacteria, not just the toxins.
- Choice C (Chemical vaccine) is incorrect as there is no such thing as a chemical vaccine; vaccines are biological preparations.
- Choice D (Genetically engineered vaccine) is incorrect because while vaccines can be genetically engineered, the specific term "genetically engineered vaccine" does not accurately describe the prophylaxis used against anthrax in this scenario.
Which of the following bacteria is known for producing a neurotoxin that causes botulism?
- A. Clostridium botulinum
- B. Clostridium perfringens
- C. Streptococcus pneumoniae
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the neurotoxin responsible for botulism. Clostridium perfringens is associated with gas gangrene, not botulism. Streptococcus pneumoniae causes pneumonia, and Neisseria gonorrhoeae causes gonorrhea, not botulism. Therefore, A is the correct choice.