Nokea
Which of the following bacteria is responsible for causing cholera?
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella enterica
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that infects the small intestine, leading to severe diarrhea and dehydration. This bacterium produces a toxin that causes the symptoms of cholera.
A: Shigella dysenteriae causes dysentery, not cholera.
C: Salmonella enterica causes food poisoning, not cholera.
D: Escherichia coli can cause food poisoning but not cholera.
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Immunity after single vaccination against tetanus - application of tetanus toxoid is:
- A. intense and usually life long
- B. of limited duration, booster vaccinations are needed
- C. infectious (non-sterile)
- D. no correct answer
Correct Answer: B
Rationale: The correct answer is B. Immunity after a single tetanus vaccination is of limited duration, usually around 10 years. Booster vaccinations are needed to maintain protection due to waning immunity over time. Choice A is incorrect as immunity is not usually lifelong. Choice C is incorrect as tetanus toxoid is a sterile vaccine and does not cause infection. Choice D is also incorrect as there is a correct answer, which is B.
A patient with a sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were catalase-negative and beta-hemolytic on blood agar. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Streptococcus pneumoniae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: Step 1: Gram-positive cocci in chains suggest Streptococcus species.
Step 2: Catalase-negative eliminates Staphylococcus aureus.
Step 3: Beta-hemolytic on blood agar matches Streptococcus pyogenes.
Step 4: Streptococcus pyogenes is a common cause of sore throat (pharyngitis).
Summary:
A: Streptococcus pyogenes - Correct due to Gram-positive cocci in chains, catalase-negative, beta-hemolytic, and common cause of sore throat.
B: Staphylococcus aureus - Incorrect due to catalase-positive.
C: Streptococcus pneumoniae - Incorrect due to alpha-hemolytic.
D: Enterococcus faecalis - Incorrect due to not being beta-hemolytic.
A patient with a sore throat and fever had a throat culture revealing Gram-positive cocci in chains. The bacteria were beta-hemolytic. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae
- C. Enterococcus faecalis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes.
1. Gram-positive cocci in chains suggest streptococci.
2. Beta-hemolytic activity indicates Streptococcus pyogenes.
3. Streptococcus pyogenes is commonly associated with sore throat (pharyngitis) and fever.
4. Streptococcus pneumoniae (choice B) is alpha-hemolytic and mainly causes pneumonia.
5. Enterococcus faecalis (choice C) is not typically associated with sore throat.
6. Staphylococcus aureus (choice D) is not commonly beta-hemolytic and is not a typical cause of pharyngitis.
Francisella tularensis is a:
- A. spore forming encapsulated gram-negative bacterium
- B. non-spore forming encapsulated gram-negative bacterium
- C. non-spore forming non-capsulated gram-negative bacterium
- D. spore forming non-capsulated gram-negative bacterium
Correct Answer: B
Rationale: The correct answer is B: non-spore forming encapsulated gram-negative bacterium. Francisella tularensis is a non-spore forming bacterium, which rules out choices A and D. It is encapsulated, which eliminates choice C. The encapsulation of the bacterium helps it evade the host immune system, leading to its pathogenicity. This encapsulated bacterium is responsible for causing the zoonotic disease tularemia in humans.
Which bacteria are capable of producing endospores?
- A. Staphylococcus aureus
- B. Clostridium botulinum
- C. Escherichia coli
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: The correct answer is B: Clostridium botulinum. This bacterium belongs to the Clostridium genus, known for its ability to produce endospores. Endospores are dormant, resistant structures that help bacteria survive harsh conditions. Staphylococcus aureus (A), Escherichia coli (C), and Neisseria gonorrhoeae (D) do not produce endospores. Staphylococcus aureus is a gram-positive bacterium known for causing various infections, but it does not form endospores. Escherichia coli is a gram-negative bacterium commonly found in the intestines of humans and animals, but it does not produce endospores. Neisseria gonorrhoeae is a gram-negative bacterium that causes the sexually transmitted infection gonorrhea, but it also does not form endospores.