Which of the following bacteria is known for causing the disease tetanus?
- A. Clostridium tetani
- B. Clostridium perfringens
- C. Streptococcus pyogenes
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Clostridium tetani. This bacterium is known for causing tetanus due to its ability to produce tetanospasmin, a neurotoxin that leads to the characteristic muscle stiffness and spasms seen in tetanus. Clostridium perfringens (Choice B) is associated with gas gangrene, Streptococcus pyogenes (Choice C) causes streptococcal infections, and Escherichia coli (Choice D) is known for causing various gastrointestinal infections. Therefore, Choices B, C, and D are incorrect as they are not the causative agents of tetanus.
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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.
For infections caused by coronaviruses is NOT true that;
- A. Most commonly associated with URT infections
- B. May be asymptomatic
- C. SARS is an atypical pneumonia that can be complicated with acute respiratory failure and can cause death
- D. Reinfections cannot be observed
Correct Answer: D
Rationale: Step-by-step rationale for why answer choice D is correct:
1. Coronaviruses can cause reinfections due to potential waning immunity.
2. Studies have shown cases of reinfections with different strains or within a short period.
3. This contradicts the notion that reinfections cannot be observed.
Summary:
A: Incorrect because some coronaviruses can cause lower respiratory tract infections.
B: Incorrect as coronaviruses can exhibit varied symptomatology including asymptomatic cases.
C: Incorrect as some coronaviruses like SARS can lead to severe pneumonia and complications.
Which of the following methods can be used for diagnosis of respiratory tract infections
- A. Culture of samples from the respiratory tract
- B. Immunofluorescence
- C. PCR
- D. All are correct
Correct Answer: D
Rationale: The correct answer is D: All are correct. Culture of samples from the respiratory tract can identify specific pathogens, Immunofluorescence can detect viral antigens, and PCR can amplify and detect specific DNA/RNA sequences. Using all methods together provides a comprehensive approach for diagnosing respiratory tract infections. Culture alone may miss fastidious organisms, Immunofluorescence has limitations in sensitivity, and PCR requires specific primers. Therefore, combining these methods increases the likelihood of accurate diagnosis by covering a range of pathogens and improving sensitivity and specificity.
Microscopy of a smear taken from the film that appeared on the peptone water 6 hours after seeding and culturing of a fecal sample in a thermostat revealed mobile gram-negative bacteria curved in form of a comma that didn't make spores or capsules. What microorganisms were revealed?
- A. Vibrios
- B. Spirochetes
- C. Clostridia
- D. Corynebacteria
Correct Answer: A
Rationale: The correct answer is A: Vibrios. Vibrios are gram-negative curved bacteria that are motile and do not form spores or capsules. The description of the bacteria in the question fits the characteristics of Vibrios. Vibrios are commonly found in aquatic environments and some species can cause gastrointestinal infections in humans.
B: Spirochetes are also gram-negative curved bacteria, but they are spiral-shaped and have unique axial filaments for motility. The description in the question does not match the characteristics of spirochetes.
C: Clostridia are gram-positive, spore-forming bacteria. The question specifically states that the bacteria are gram-negative and do not form spores, ruling out Clostridia.
D: Corynebacteria are gram-positive, non-spore-forming bacteria. The description in the question does not match the characteristics of Corynebacteria.
Which of the following bacteria can produce endotoxins that 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 because all of the mentioned bacteria (Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa) are gram-negative bacteria that produce endotoxins in their cell walls. Endotoxins are released when the bacteria are destroyed, leading to the activation of the immune system and potentially causing septic shock. Escherichia coli and Salmonella enterica are common causes of gastrointestinal infections, while Pseudomonas aeruginosa is known for causing infections in immunocompromised individuals. Therefore, all three bacteria can produce endotoxins that contribute to septic shock. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that lead to septic shock.