The optimal specimen for identifying the etiologic agent in a prosthetic joint infection (PJI) is a joint aspirate (synovial fluid). This is because:
* It provides direct access to the infected site without contamination from external sources.
* It allows for accurate microbiologic culture, Gram stain, and leukocyte count analysis.
Why the Other Options Are Incorrect?
* A. Blood - Blood cultures may help detect hematogenous spread but are not the best sample for identifying localized prosthetic joint infections.
* B. Wound drainage - Wound cultures often contain contaminants from surrounding skin flora and do not accurately reflect joint space infection.
* D. Sinus tract tissue - Cultures from sinus tracts often represent colonization rather than the primary infecting organism.
CBIC Infection Control Reference
APIC guidelines confirm that joint aspirate is the most reliable specimen for diagnosing prosthetic joint infections.