Antimicrobials — MCQs

Antituberculosis treatment is started. Two months later, the patient comes to the physician for a follow-up examination. The patient feels well. She reports that she has had tingling and bilateral numbness of her feet for the past 6 days. Her vital signs are within normal limits. Her lips are dry, scaly, and slightly swollen. Neurologic examination shows decreased sensation to pinprick and light touch over her feet, ankles, and the distal portion of her calves. Laboratory studies show: Leukocyte count 7400 /mm3 RBC count 2.9 million/mm3 Hemoglobin 10.8 g/dL Hematocrit 30.1% Mean corpuscular volume 78 fL Mean corpuscular hemoglobin 24.2 pg/cell Platelet count 320,000/mm3 Serum Glucose 98 mg/dL Alanine aminotransferase (ALT) 44 U/L Aspartate aminotransferase (AST) 52 U/L Administration of which of the following is most likely to have prevented this patient's neurological symptoms?

A 62-year-old woman presents to the clinic with a lacerated wound on her left forearm. She got the wound accidentally when she slipped in her garden and scraped her hand against some nails sticking out of the fence. The patient has rheumatoid arthritis and takes methylprednisolone 16 mg/day. She cannot recall her vaccination history. On physical examination her blood pressure is 140/95 mm Hg, heart rate is 81/min, respiratory rate is 16/min, and temperature is 36.9°C (98.4°F). The wound is irregularly shaped and lacerated and measures 4 × 5 cm with a depth of 0.5 cm. It is contaminated with dirt. The physician decides to administer both the tetanus toxoid and immunoglobulin after wound treatment. What is true regarding the tetanus prophylaxis in this patient?

A cell biologist is studying the activity of a novel chemotherapeutic agent against a cancer cell line. After incubation with the agent and cell detachment from the tissue culture plate, the DNA is harvested from the cells and run on a gel. Of note, there are large bands at every multiple of 180 base pairs on the gel. Which of the following explains the pathophysiology of this finding?

A 39-year-old man comes to the physician for a follow-up examination. He was diagnosed with latent tuberculosis infection 3 months ago. He has had generalized fatigue and dyspnea on exertion for the past 6 weeks. He does not smoke and drinks 2–3 beers on weekends. Vital signs are within normal limits. Examination shows conjunctival pallor. Laboratory studies show: Hemoglobin 7.8 g/dL Mean corpuscular volume 72 μm3 Red cell distribution width 17% (N = 13–15) Reticulocyte count 0.7% Leukocyte count 6,800/mm3 Platelet count 175,000/mm3 Serum Creatinine 0.8 mg/dL Iron 246 μg/dL Ferritin 446 ng/mL Total iron-binding capacity 212 μg/dL (N = 250–450) Which of the following is the most likely cause of this patient's symptoms?

A 65-year-old G4P4 woman presents to her primary care physician complaining of a breast lump. She reports that she felt the lump while conducting a breast self-examination. Her past medical history is notable for endometrial cancer status post radical hysterectomy. She takes aspirin and fish oil. The patient drinks 3-4 alcoholic beverages per day and has a distant smoking history. Her temperature is 98.6°F (37°C), blood pressure is 130/75 mmHg, pulse is 90/min, and respirations are 18/min. A firm palpable mass in the upper outer quadrant of the right breast is noted on physical exam. Further workup reveals invasive ductal adenocarcinoma. She eventually undergoes radical resection and is started on a medication that is known to inhibit thymidylate synthetase. This patient is at increased risk for which of the following medication adverse effects?

A 26-year-old male currently undergoing standard therapy for a recently diagnosed active tuberculosis infection develops sudden onset of fever and oliguria. Laboratory evaluations demonstrate high levels of eosinophils in both the blood and urine. Which of the following is most likely responsible for the patient's symptoms?

A 65-year-old obese woman presents with changes in her left breast. The patient states that, about a month ago, she noticed that she was able to feel a hard mass in the upper outer quadrant of her left breast, which has not gone away. In addition, her nipple and skin overlying the breast have started to look different. Past medical history is significant for polycystic ovarian syndrome (PCOS) and hypertension, well-managed with lisinopril. The patient has never been pregnant. Menopause was at age 53. Family history is significant for breast cancer in her mother at age 55, and her father who died of lung cancer at age 52. A review of systems is significant for a 13.6 kg (30 lb) weight loss in the last 2 months despite no change in diet or activity. Vitals include: temperature 37.0°C (98.6°F), blood pressure 120/75 mm Hg, pulse 97/min, respiratory rate 16/min, and oxygen saturation 99% on room air. Physical examination is significant for a palpable, hard, fixed mass in the upper outer quadrant of the left breast, as well as nipple retraction and axillary lymphadenopathy. Mammography of the left breast reveals a spiculated mass in the upper outer quadrant. A biopsy confirms invasive ductal carcinoma. Molecular analysis reveals that the tumor cells are positive for HER2/neu receptor, which is associated with a poor prognosis. Which of the following is indicated as first-line targeted therapy for this patient's treatment?

A 23-year-old man comes to the physician because of a 1-week history of muscle ache, fatigue, and fever that occurs every 2 days. He recently returned from a trip to Myanmar. A peripheral blood smear shows erythrocytes with brick-red granules. The physician recommends a combination of two antimicrobial drugs after confirming normal glucose-6-phosphate dehydrogenase activity. Which of the following is the most appropriate rationale for dual therapy?

A 25-year-old medical student is doing an international health elective in the Amazon River basin studying tropical disease epidemiology. As part of his pre-trip preparation, he wants to be protected from malaria and is researching options for prophylaxis. Which of the following agents should be avoided for malarial prophylaxis in this patient?

A 65-year-old man presents with a small painless ulcer with a raised border on his right forearm which has persisted for the last 3 weeks. His past history is significant for 3 occurrences of basal cell carcinoma on different areas of the body during the last 4 years, which have all been surgically excised. The morphology of the present lesion is also highly suggestive of basal cell carcinoma. The patient says that, if the lesion is a basal cell carcinoma, he does not want to undergo biopsy and surgery if it can be avoided. The patient is prescribed a cream, which is FDA-approved for the treatment of small superficial basal cell carcinomas in low-risk areas. The cream contains a chemotherapeutic agent, which is an antimetabolite and an S-phase-specific anticancer drug. Which of the following best explains the mechanism of action of this cream?