Nokea
Rheumatic fever is usually a complication of a(n) __________ infection.
- A. Escherichia coli
- B. Streptococcus pyogenes
- C. Staphylococcus epidermidis
- D. Staphylococcus aureus
Correct Answer: B
Rationale: Rationale:
1. Streptococcus pyogenes is the causative agent of strep throat.
2. If untreated, strep throat can lead to rheumatic fever.
3. Rheumatic fever is an autoimmune complication of streptococcal infections.
4. E. coli, S. epidermidis, and S. aureus are not typically associated with rheumatic fever.
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A 45-year-old patient complains of body temperature rise up to 40oC, general weakness, headache, painfulness and spastic muscle contractions around the wound in the shin. He received this wound 5 days ago when working in his garden. He requested no medical care back then. What wound infection can be suspected?
- A. Tetanus
- B. Anthrax
- C. Erysipelas
- D. Gram-positive
Correct Answer: A
Rationale: The correct answer is A: Tetanus. The patient's symptoms of muscle contractions, fever, and wound history suggest tetanus, caused by Clostridium tetani bacteria commonly found in soil. The spastic muscle contractions around the wound are classic for tetanus due to the neurotoxin produced by the bacteria. General weakness and headache are also common symptoms.
B: Anthrax is unlikely as it presents with different symptoms such as skin lesions, respiratory symptoms, and gastrointestinal symptoms.
C: Erysipelas is characterized by red, swollen patches on the skin, not consistent with the symptoms described.
D: Gram-positive is not a specific diagnosis but a broad category of bacteria. Tetanus is caused by Clostridium tetani, which is a Gram-positive bacterium, but this choice does not provide a specific infection diagnosis.
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.
Which of the following bacteria produce a toxin that inhibits protein synthesis?
- A. Shigella dysenteriae
- B. Escherichia coli
- C. Clostridium tetani
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Shigella dysenteriae. This bacterium produces Shiga toxin, which inhibits protein synthesis by inactivating the ribosomes. Shigella dysenteriae is known to cause severe gastrointestinal infections.
Choice B: Escherichia coli typically does not produce toxins that inhibit protein synthesis. E. coli strains may produce toxins that cause diarrhea.
Choice C: Clostridium tetani produces tetanospasmin toxin, which affects the nervous system but does not inhibit protein synthesis.
Choice D: Staphylococcus aureus produces toxins like enterotoxins and exotoxins but these toxins do not directly inhibit protein synthesis.
Which type of bacteria have an outer membrane containing lipopolysaccharides (LPS)?
- A. Gram-positive bacteria
- B. Gram-negative bacteria
- C. Both Gram-positive and Gram-negative bacteria
- D. Neither Gram-positive nor Gram-negative bacteria
Correct Answer: B
Rationale: The correct answer is B: Gram-negative bacteria. Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS). In the Gram staining technique, these bacteria appear pink/red due to the thin peptidoglycan layer, which allows the crystal violet stain to be washed out, revealing the safranin counterstain. Gram-positive bacteria (choice A) have a thick peptidoglycan layer but lack an outer membrane with LPS. Choice C is incorrect since only Gram-negative bacteria possess LPS in their outer membrane. Choice D is incorrect as all bacteria can be classified as either Gram-positive or Gram-negative based on their cell wall structure.
Which bacteria produce endotoxins that can cause septic shock?
- A. Escherichia coli
- B. Salmonella enterica
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D. Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa all produce endotoxins that can lead to septic shock. Endotoxins are part of the outer membrane of Gram-negative bacteria and can trigger a systemic inflammatory response if released into the bloodstream. E. coli and Salmonella are common causes of bacterial infections that can lead to septic shock, while P. aeruginosa is a known opportunistic pathogen that can produce endotoxins. Therefore, all three bacteria can cause septic shock by releasing endotoxins. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that contribute to the development of septic shock.