Microbiology An Evolving Science Test Bank

Correct Answer: D

Rationale: The correct answer is D: Amebiasis. The patient's symptoms of gastrointestinal disturbance and liver abscess are indicative of an infection with Entamoeba histolytica, the protozoan parasite responsible for amebiasis. The patient's travel history to an African country also increases the likelihood of contracting this disease, as it is more prevalent in tropical regions. Toxoplasmosis (A) is primarily associated with exposure to cat feces, Leishmaniasis (B) is transmitted through sandfly bites, and Malaria (C) is caused by Plasmodium parasites transmitted through mosquito bites. Therefore, these options are incorrect given the patient's presentation and travel history.

Correct Answer: A

Rationale: The correct answer is A: Chingamin (also known as Chloroquine). Chingamin is the drug of choice for chemoprophylaxis of malaria in regions with high risk. It is effective against Plasmodium falciparum, the most common malaria parasite. Chingamin is well-tolerated, affordable, and has a long track record of use. Sulfalen (Choice B) is not commonly used for malaria prophylaxis. Tetracycline (Choice C) is not recommended for malaria prophylaxis due to poor efficacy and resistance development. Metronidazole (Choice D) is not effective against malaria parasites.

Correct Answer: B

Rationale: The correct answer is B: CMV. Patients after allogeneic stem cell transplantation are monitored for CMV reactivation due to its potential to cause severe complications in immunocompromised individuals. CMV can lead to organ damage and even mortality in these patients. Monitoring for CMV reactivation allows for early detection and prompt intervention. Incorrect Choices: A: HAV - Hepatitis A virus reactivation is not commonly monitored in post-transplant patients. C: Rubella virus - Rubella is not a common concern for reactivation in this patient population. D: Measles virus - Measles reactivation is not typically monitored in these patients.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. This bacterium is responsible for causing tetanus due to its production of tetanus toxin. Clostridium perfringens (B) causes gas gangrene, Streptococcus pyogenes (C) causes strep throat and skin infections, and Escherichia coli (D) is a common gut bacteria that can cause food poisoning but not tetanus.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. The presence of Gram-positive cocci in chains suggests a streptococcal infection. Beta-hemolysis indicates the production of a hemolysin that lyses red blood cells, a characteristic of Streptococcus pyogenes. This bacterium is known to cause strep throat and can present with fever and sore throat. Summary: - B: Streptococcus pneumoniae is a common cause of pneumonia but typically appears as lancet-shaped cocci, not in chains. - C: Staphylococcus aureus is a gram-positive cocci in clusters, not chains, and is not typically beta-hemolytic. - D: Enterococcus faecalis is a gram-positive cocci that are part of the normal gut flora and are not typically beta-hemolytic or found in chains.