A hospital infection control team investigates an increase in CLABSI (central line-associated bloodstream infection) rates. Blood cultures drawn through a central venous catheter (CVC) and peripheral vein simultaneously. CVC cultures turn positive at 2 hours, peripheral at 5 hours. What criterion does this differential time to positivity (DTP) satisfy for catheter-related bloodstream infection (CRBSI) diagnosis without removing the line?
- A DTP >1 hour of CVC positivity before peripheral supports CRBSI diagnosis
- B DTP is not a validated criterion; CRBSI requires tip culture ≥15 CFU by semiquantitative method
- C DTP >30 minutes satisfies the CRBSI criterion
- D DTP >2 hours of CVC positivity before peripheral (here exactly 2h; ≥2h is the threshold) — line removal not needed for diagnosis ✓
Explanation
Differential time to positivity (DTP) is a validated non-removal diagnostic method for CRBSI: if the CVC blood culture turns positive ≥2 hours before the peripheral blood culture (drawn simultaneously with equal volumes), it confirms intraluminal catheter biofilm as the source, with specificity ~91% and sensitivity ~82%. In this case DTP = 3 hours (5h − 2h), meeting the ≥2h criterion. IDSA criteria also include quantitative blood cultures (CVC:peripheral colony count ratio ≥5:1). Catheter tip culture (Maki roll plate ≥15 CFU) is used when catheter is removed.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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