Molecular diagnostics · USMLE Step 1

Why is PCR-based molecular diagnostics often favored for detecting infectious agents compared to traditional culture methods?

  1. PCR also reports antibiotic susceptibility results
  2. PCR detects pathogen DNA even when organisms are non-viable
  3. PCR is essentially immune to sample contamination
  4. PCR strictly requires live, replicating pathogens
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Correct answer: PCR detects pathogen DNA even when organisms are non-viable

PCR amplifies genetic material directly from samples, enabling detection of pathogens even if they’re non-viable or present in low numbers, which is especially useful for fastidious or slow-growing organisms.

Difficulty: Medium Question 8 of 21

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