A microbiologist is involved in research on the emergence of a novel virus, X, which caused a recent epidemic in his community. After studying the structure of the virus, he proposes a hypothesis: Virus X developed from viruses A and B. He suggests that viruses A and B could co-infect a single host cell. During the growth cycles of the viruses within the cells, a new virion particle is formed, which contains the genome of virus A; however, its coat contains components of the coats of both viruses A and B. This new virus is identical to virus X, which caused the epidemic. Which of the following phenomena is reflected in the hypothesis proposed by the microbiologist?
AComplementation
BPhenotypic mixing
CGenetic reassortment
DGenetic recombination
EAntigenic shift
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 42-year-old woman with a history of multiple sclerosis and recurrent urinary tract infections comes to the emergency department because of flank pain and fever. Her temperature is 38.8°C (101.8°F). Examination shows left-sided costovertebral angle tenderness. She is admitted to the hospital and started on intravenous vancomycin. Three days later, her symptoms have not improved. Urine culture shows growth of Enterococcus faecalis. Which of the following best describes the most likely mechanism of antibiotic resistance in this patient?
AIncreased efflux across bacterial cell membranes
BProduction of beta-lactamase
CAlteration of penicillin-binding proteins
DAlteration of peptidoglycan synthesis
EAlteration of ribosomal targets
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