A 57-year-old woman is brought to the emergency department because of crampy abdominal pain and foul-smelling, watery diarrhea. One week ago, she underwent treatment of cellulitis with clindamycin. She has developed shortness of breath and urticaria after treatment with vancomycin in the past. Her temperature is 38.4°C (101.1°F). Abdominal examination shows mild tenderness in the left lower quadrant. Her leukocyte count is 12,800/mm3. An enzyme immunoassay is positive for glutamate dehydrogenase antigen and toxins A and B. Which of the following is the mechanism of action of the most appropriate pharmacotherapy for this patient's condition?
ABlocking of protein synthesis at 50S ribosomal subunit
BInhibition of cell wall peptidoglycan formation
CInhibition of RNA polymerase sigma subunit
DInhibition of bacterial topoisomerases II and IV
EGeneration of toxic free radical metabolites
A 37-year-old woman with a history of anorectal abscesses complains of pain in the perianal region. Physical examination reveals mild swelling, tenderness, and erythema of the perianal skin. She is prescribed oral ampicillin and asked to return for follow-up. Two days later, the patient presents with a high-grade fever, syncope, and increased swelling. Which of the following would be the most common mechanism of resistance leading to the failure of antibiotic therapy in this patient?
AIntrinsic absence of a target site for the drug
BUse of an altered metabolic pathway
CProduction of beta-lactamase enzyme
DAltered structural target for the drug
EDrug efflux pump
A 68-year-old man comes to the physician because of headache, fatigue, and nonproductive cough for 1 week. He appears pale. Pulmonary examination shows no abnormalities. Laboratory studies show a hemoglobin concentration of 9.5 g/dL and an elevated serum lactate dehydrogenase concentration. A peripheral blood smear shows normal red blood cells that are clumped together. Results of cold agglutinin titer testing show a 4-fold elevation above normal. An x-ray of the chest shows diffuse, patchy infiltrates bilaterally. Treatment is begun with an antibiotic that is also used to promote gut motility. Which of the following is the primary mechanism of action of this drug?
AInhibition of bacterial RNA polymerase
BInhibition of folic acid synthesis
CFree radical creation within bacterial cells
DInhibition of transpeptidase cross-linking at the cell wall
EInhibition of peptide translocation at the 50S ribosomal subunit
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