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Question

Difficulty: MediumInfectious Diseases

Match each clinical presentation with the most appropriate first-line targeted or empiric antimicrobial therapy.

  • A 24-year-old camper in North Carolina develops fever, severe myalgias, headache, and a petechial rash originating on the wrists and ankles.Oral doxycycline
  • A 32-year-old intravenous drug user presents with high fever, a new tricuspid regurgitation murmur, and scattered cavitary lung lesions on chest imaging.Intravenous vancomycin
  • A 19-year-old college dormitory resident presents with sudden fever, nuchal rigidity, and a rapidly spreading purpuric rash on the lower extremities.Intravenous ceftriaxone
  • A 55-year-old farmer from Ohio presents with chronic cough, low-grade fever, and well-circumscribed verrucous skin lesions; microscopy shows broad-based budding yeast.Oral itraconazole

Answer

The camper with wrist/ankle rash requires oral doxycycline (RMSF); the IV drug user with right-sided endocarditis requires intravenous vancomycin (MRSA); the college student with purpuric meningitis requires intravenous ceftriaxone (Meningococcus); and the farmer with broad-based budding yeast requires oral itraconazole (Blastomycosis).
Each pathogen or clinical syndrome has a highly specific first-line antimicrobial agent guided by local epidemiology, resistance patterns, and pharmacokinetics (such as CNS penetration for meningitis or intracellular activity for rickettsial disease).

Step-by-Step Solution

1
Analyze the tick-borne disease vignette.
Identify Rocky Mountain Spotted Fever based on the North Carolina location and centripetal petechial rash starting on extremities.
Recognizing the classic triad of fever, headache, and distal rash points directly to Rickettsia rickettsii, which must be treated with doxycycline.
2
Analyze the infective endocarditis vignette.
Identify right-sided (tricuspid) endocarditis complicated by septic pulmonary emboli in an intravenous drug user.
Staphylococcus aureus is the most common pathogen in this demographic, necessitating robust empiric MRSA coverage with vancomycin.
3
Analyze the central nervous system infection vignette.
Identify meningococcal meningitis based on the demographic (dormitory resident) and characteristic purpuric rash.
Neisseria meningitidis is a leading cause of bacterial meningitis in this age group and requires a third-generation cephalosporin like ceftriaxone for optimal CNS penetration and coverage.
4
Analyze the systemic fungal infection vignette.
Identify Blastomyces dermatitidis based on geography (Ohio), verrucous skin lesions, and broad-based budding yeast morphology.
Matching the morphologic description to the pathogen determines the choice of an azole antifungal, specifically itraconazole, for non-life-threatening systemic disease.

Key Concept

Selection of optimal empiric or targeted antimicrobial therapy based on clinical presentation, epidemiologic risk factors, and microbiological clues.
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Topics

Infectious Diseases

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