Nokea
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.
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A patient with severe abdominal pain and diarrhea had a stool sample cultured. The bacteria were Gram-negative rods that did not ferment lactose. What is the most likely causative agent?
- A. Salmonella enterica
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: A
Rationale: The correct answer is A: Salmonella enterica. This is because Salmonella are Gram-negative rods that do not ferment lactose, which fits the description in the question. Additionally, Salmonella is a common cause of severe abdominal pain and diarrhea. Shigella dysenteriae is a Gram-negative rod that also causes severe diarrhea but it does not share the characteristic of not fermenting lactose. Escherichia coli is a Gram-negative rod that does ferment lactose. Proteus vulgaris is also a Gram-negative rod but it is not commonly associated with severe abdominal pain and diarrhea, making it an unlikely causative agent in this scenario.
Which of the following diseases is transmitted via aerosols?
- A. Psittacosis
- B. Shigellosis
- C. Leptospirosis
- D. Giardiasis
Correct Answer: A
Rationale: The correct answer is A: Psittacosis. This disease is transmitted via aerosols containing dried bird droppings or respiratory secretions from infected birds. When these aerosols are inhaled, the bacteria causing psittacosis enter the respiratory system and infect the individual.
- B: Shigellosis is transmitted through contaminated food or water, not via aerosols.
- C: Leptospirosis is transmitted through contact with water, soil, or food contaminated with the urine of infected animals, not via aerosols.
- D: Giardiasis is transmitted through ingesting contaminated food or water, not via aerosols.
Therefore, Psittacosis is the only disease in the list that is transmitted via aerosols, making it the correct answer.
Which of the following bacteria is known for causing the disease known as leprosy?
- A. Mycobacterium leprae
- B. Clostridium perfringens
- C. Streptococcus pneumoniae
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: Step-by-step rationale:
1. Mycobacterium leprae is the correct answer as it is the bacteria known to cause leprosy.
2. Clostridium perfringens is incorrect as it is associated with gas gangrene.
3. Streptococcus pneumoniae is incorrect as it is commonly linked to pneumonia and meningitis.
4. Neisseria gonorrhoeae is incorrect as it causes gonorrhea, a sexually transmitted infection.
In summary, Mycobacterium leprae is the only bacteria among the choices specifically known to cause leprosy, making it the correct answer.
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.
The function of beta-lactamase in bacteria is to:
- A. Break down antibiotics like penicillin
- B. Enhance protein synthesis
- C. Facilitate DNA replication
- D. Transport nutrients
Correct Answer: A
Rationale: The correct answer is A: Break down antibiotics like penicillin. Beta-lactamase is an enzyme produced by bacteria to inactivate beta-lactam antibiotics like penicillin by breaking the beta-lactam ring. This mechanism helps bacteria resist the antibiotic's effects. The other choices are incorrect because beta-lactamase does not enhance protein synthesis, facilitate DNA replication, or transport nutrients. It specifically targets and deactivates beta-lactam antibiotics, making choice A the most appropriate answer.