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A patient presented with a painful, swollen lymph node, and bacteremia. A Gram-negative rod with a characteristic safety pin appearance was observed. What is the causative agent?
- A. Yersinia pestis
- B. Clostridium tetani
- C. Brucella melitensis
- D. Pasteurella multocida
Correct Answer: A
Rationale: Step 1: Gram-negative rod with safety pin appearance indicates bipolar staining.
Step 2: Yersinia pestis is a Gram-negative rod causing bubonic plague.
Step 3: Y. pestis has bipolar staining due to its unique F1 capsule.
Step 4: The swollen lymph node and bacteremia are consistent with bubonic plague.
Step 5: Therefore, the correct answer is A: Yersinia pestis.
Summary:
- B: Clostridium tetani causes tetanus, not characterized by a safety pin appearance.
- C: Brucella melitensis causes brucellosis, not characterized by a safety pin appearance.
- D: Pasteurella multocida causes animal bites infections, not characterized by a safety pin appearance.
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Methods typically used to diagnose bacterial infections of the reproductive system include:
- A. microscopic examination of discharge from infected organ and microscopic examination of urine for organisms
- B. biopsy of infected tissue and use of selective media
- C. microscopic examination of fecal sample and protein test of urine
- D. antibody agglutination test and coagulation test
Correct Answer: A
Rationale: Step-by-step rationale for choice A being correct:
1. Microscopic examination of discharge from infected organ allows direct visualization of bacteria causing the infection.
2. Microscopic examination of urine for organisms can help identify any bacteria present in the urinary tract.
3. Both methods are specific for diagnosing bacterial infections in the reproductive system.
Summary:
- Choice B is incorrect as biopsy is invasive and not typically used for diagnosing bacterial infections.
- Choice C is incorrect as fecal samples and urine protein tests are not relevant for diagnosing bacterial infections in the reproductive system.
- Choice D is incorrect as antibody agglutination and coagulation tests are not primary methods for diagnosing bacterial infections in the reproductive system.
UN volunteers have arrived in Nigeria to assist the locals in aftermath of earthquakes. What drug should they prescribe for individual chemoprophylaxis of malaria?
- A. Chingamin
- B. Pyrantel
- C. Pyrimethamine (Chloridinum)
- D. Primaquine
Correct Answer: D
Rationale: The correct answer is D: Primaquine. Primaquine is used for individual chemoprophylaxis of malaria caused by Plasmodium vivax and Plasmodium ovale. It is effective in preventing the relapse of these malaria species by eliminating the liver forms of the parasites. Chingamin (A) is not a commonly used drug for malaria prophylaxis. Pyrantel (B) is an anthelmintic drug used for treating parasitic worm infections, not malaria. Pyrimethamine (Chloridinum) (C) is primarily used in combination with sulfadoxine for treating uncomplicated malaria, not for chemoprophylaxis.
Lysozyme acts on the bacterial:
- A. cytoplasm
- B. cell wall
- C. nucleus
- D. capsule
Correct Answer: B
Rationale: The correct answer is B: cell wall. Lysozyme is an enzyme that targets the cell wall of bacteria by breaking down the peptidoglycan layer, leading to bacterial cell lysis. This action disrupts the structural integrity of the bacteria, ultimately causing their death. Choices A, C, and D are incorrect because lysozyme does not target the cytoplasm, nucleus, or capsule of bacteria. The primary function of lysozyme is to act on the cell wall, making option B the correct answer in this context.
A wound swab from a patient with severe tissue infection revealed Gram-positive rods in chains producing gas. The bacteria were spore-forming. What is the causative agent?
- A. Clostridium perfringens
- B. Bacillus anthracis
- C. Clostridium tetani
- D. Pseudomonas aeruginosa
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. This bacterium is a Gram-positive rod that forms chains and produces gas due to its ability to ferment carbohydrates. It is also spore-forming, which helps it survive harsh conditions. Clostridium perfringens is commonly associated with severe tissue infections and gas gangrene.
Choice B: Bacillus anthracis is also a spore-forming Gram-positive rod but is not typically associated with gas production or severe tissue infections.
Choice C: Clostridium tetani is a spore-forming bacterium that causes tetanus, not severe tissue infections with gas production.
Choice D: Pseudomonas aeruginosa is a Gram-negative bacterium and does not fit the description provided in the question.
A patient with severe abdominal pain had a stool culture revealing non-lactose-fermenting, Gram-negative rods that produce gas in nutrient broth. What is the most likely causative agent?
- A. Salmonella enterica
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: D
Rationale: The correct answer is D: Proteus vulgaris. This is because Proteus species are non-lactose-fermenting, Gram-negative rods that produce gas in nutrient broth. They are known to cause severe abdominal pain due to their ability to invade the intestinal mucosa.
A: Salmonella enterica is a lactose-fermenting organism and typically does not produce gas in nutrient broth.
B: Shigella dysenteriae is a lactose-negative organism but does not produce gas in nutrient broth.
C: Escherichia coli is a lactose-fermenting organism and does not typically produce gas in nutrient broth.
In summary, the presence of non-lactose-fermenting, gas-producing Gram-negative rods points towards Proteus vulgaris as the most likely causative agent of the severe abdominal pain.