Antimicrobials — MCQs

A 31-year-old male traveler in Thailand experiences fever, headache, and excessive sweating every 48 hours. Peripheral blood smear shows trophozoites and schizonts indicative of Plasmodia infection. The patient is given chloroquine and primaquine. Primaquine targets which of the following Plasmodia forms:

A 71-year-old man with colon cancer presents to his oncologist because he has been experiencing photosensitivity with his current chemotherapeutic regimen. During the conversation, they decide that his symptoms are most likely a side effect of the 5-fluorouracil he is currently taking and decide to replace it with another agent. The patient is curious why some organs appear to be especially resistant to chemotherapy whereas others are particularly susceptible to chemotherapy. Which of the following cell types would be most resistant to chemotherapeutic agents?

A 20-year-old man presents with a tremor involving his upper limbs for the past 3 weeks. He says his symptoms have been progressively worsening. Past medical history is significant for 2 episodes of undiagnosed jaundice over the last year. No significant family history. His temperature is 36.9°C (98.4°F), the pulse is 82/min, the blood pressure is 116/78 mm Hg, and the respiratory rate is 12/min. On physical examination, there is excessive salivation, and he has an expressionless face. He has an ataxic gait accompanied by asymmetric resting and kinetic tremors. Hepatomegaly is evident. There is a greenish-gold limbal ring in both corneas. After laboratory findings confirm the diagnosis, the patient is prescribed a medication that he is warned may worsen his tremors. The patient is also instructed to return in a week for a complete blood count and urinalysis. Which of the following additional adverse effects may be expected in this patient while taking this medication?

A 55-year-old man, who was recently diagnosed with tuberculosis, presents to his primary care provider as part of his routine follow-up visit every month. He is currently in the initial phase of anti-tubercular therapy. His personal and medical histories are relevant for multiple trips to Southeast Asia as part of volunteer activities and diabetes of 5 years duration, respectively. A physical examination is unremarkable except for a visual abnormality on a color chart; he is unable to differentiate red from green. The physician suspects the visual irregularity as a sign of toxicity due to one of the drugs in the treatment regimen. Which of the following is the mechanism by which this medication acts in the treatment of Mycobacterium tuberculosis?

A 32-year-old man is brought to the emergency department with fever, dyspnea, and impaired consciousness. His wife reports that he has also had an episode of dark urine today. Two weeks ago, he returned from a trip to the Republic of Congo. His temperature is 39.4°C (103°F), pulse is 114/min, and blood pressure is 82/51 mm Hg. Physical examination shows scleral icterus. Decreased breath sounds and expiratory crackles are heard on auscultation of the lungs bilaterally. His hemoglobin concentration is 6.3 g/dL. A blood smear shows red blood cells with normal morphology and ring-shaped inclusions. Further laboratory testing shows normal rates of NADPH production. Which of the following is the most appropriate pharmacotherapy for this patient?

A 55-year-old male with a 60 pack-year smoking history presents to his oncologist for ongoing management of his recently diagnosed small cell lung cancer. His oncologist discusses several options and decides to start the chemotherapeutic medication, etoposide. The patient is warned that one side effect of this drug is myelosuppression so he should be vigilant for development of any infectious symptoms. The beneficial effect of this drug in treating cancer is most likely due to which of the following effects?

A 23-year-old woman is brought to the emergency department 30 minutes after stepping on a piece of broken glass. Physical examination shows a 3-cm, ragged laceration on the plantar aspect of the left foot. The physician uses hydrogen peroxide to clean the wound. Which of the following is the most likely mechanism of action of this disinfectant?

A 19-year-old woman presents with abdominal pain and diarrhea for the last week. She has missed 3 days of school and is extremely stressed about the effect of this absence on her academic performance. She has had a couple of similar though less intense episodes in the past. She says that the diarrhea alternates with constipation and is associated with bloating and flatus. She describes the abdominal pain as spasmodic and episodic, sometimes radiating to the legs, with each episode lasting for 10–15 minutes and relieved by defecation. The patient denies any change in the color of her feces, increased frequency of urination or burning during micturition, loss of appetite or weight loss. No significant past medical history. No significant family history. Physical examination is unremarkable. Laboratory investigations are normal. Which of the following would the best choice to manage the diarrheal symptoms in this patient?

A 27-year-old male presents to urgent care complaining of pain with urination. He reports that the pain started 3 days ago. He has never experienced these symptoms before. He denies gross hematuria or pelvic pain. He is sexually active with his girlfriend, and they consistently use condoms. When asked about recent travel, he admits to recently returning from a “boys' trip" in Cancun where he had unprotected sex 1 night with a girl he met at a bar. The patient’s medical history includes type I diabetes that is controlled with an insulin pump. His mother has rheumatoid arthritis. The patient’s temperature is 99°F (37.2°C), blood pressure is 112/74 mmHg, and pulse is 81/min. On physical examination, there are no lesions of the penis or other body rashes. No costovertebral tenderness is appreciated. A urinalysis reveals no blood, glucose, ketones, or proteins but is positive for leukocyte esterase. A urine microscopic evaluation shows a moderate number of white blood cells but no casts or crystals. A urine culture is negative. Which of the following is the most likely cause for the patient’s symptoms?

A 23-year-old woman comes to the emergency department because of a diffuse, itchy rash and swollen face for 6 hours. That morning, she was diagnosed with an abscess of the lower leg. She underwent treatment with incision and drainage as well as oral antibiotics. She has no history of serious illness. She is not in acute distress. Her temperature is 37.2°C (99°F), pulse is 78/min, and blood pressure is 128/84 mm Hg. Physical examination shows mild swelling of the eyelids and lips. There are multiple erythematous patches and wheals over her upper extremities, back, and abdomen. The lungs are clear to auscultation. Cardiac examination shows no abnormalities. After discontinuing all recently administered drugs and beginning continuous vital sign monitoring, which of the following is the most appropriate next step in management?