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Difficulty: HardInfectious Diseases

Match each patient's clinical presentation and diagnostic findings with the most appropriate targeted antimicrobial regimen.

  • A 24-year-old pregnant patient at 10 weeks gestation evaluated in the outpatient clinic for an expanding annular rash with central clearing after an Appalachian trail hike.Oral amoxicillin monotherapy
  • A 65-year-old male admitted to the cardiovascular intensive care unit with a mechanical aortic valve, presenting with fever and blood cultures growing methicillin-resistant Staphylococcus aureus (MRSA).Intravenous vancomycin, gentamicin, and rifampin
  • A 35-year-old patient with untreated HIV and a CD4 count of 40 cells/mm³ evaluated in the infectious disease clinic for fever, weight loss, and blood cultures yielding Mycobacterium avium complex.Oral clarithromycin and ethambutol
  • A 52-year-old female in the emergency department with acute pyelonephritis and septic shock; urine culture reveals Escherichia coli resistant to third-generation cephalosporins and aztreonam.Intravenous meropenem monotherapy

Answer

The correct matches align the pregnant patient with Lyme disease to amoxicillin, the MRSA prosthetic valve endocarditis to vancomycin/gentamicin/rifampin, the disseminated MAC infection to a macrolide/ethambutol, and the ESBL pyelonephritis to a carbapenem.
Each correct pairing directly matches a complex infectious disease scenario with its definitive, guideline-directed antimicrobial regimen, carefully accounting for resistance mechanisms (ESBL), anatomical challenges (prosthetic biofilms), multidrug necessities (mycobacteria), and host safety factors (pregnancy).

Step-by-Step Solution

1
Identify the underlying pathogen and any host-specific contraindications for the pregnant patient.
Pathogen is Borrelia burgdorferi (Lyme disease). Doxycycline is contraindicated in pregnancy, making amoxicillin the correct choice.
Avoidance of teratogenic effects while ensuring effective clearance of the spirochete.
2
Determine the necessary regimen components for prosthetic valve endocarditis caused by MRSA.
Requires vancomycin for MRSA coverage, rifampin for biofilm penetration, and gentamicin for synergy.
Monotherapy is insufficient to eradicate biofilm-associated staphylococcal infections on foreign bodies.
3
Select the appropriate targeted therapy for disseminated MAC in advanced HIV.
A multi-drug regimen comprising a macrolide (clarithromycin) and ethambutol.
Dual therapy is required to adequately treat mycobacterial infections and prevent the rapid emergence of resistance.
4
Interpret the resistance pattern of the E. coli in the patient with pyelonephritis and septic shock.
The resistance profile is pathognomonic for an ESBL-producing organism, necessitating treatment with a carbapenem like meropenem.
ESBL-producing enterobacteriaceae readily hydrolyze penicillins, most cephalosporins, and aztreonam, making carbapenems the safest and most effective option for severe infections.

Key Concept

Selection of targeted antimicrobial therapy must account for pathogen resistance profiles, biofilm presence, and host-specific contraindications.
Estimated Time:2m 0s
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Infectious Diseases

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