A patient in the medical ICU develops fever on day 5 of central venous catheter placement. Blood cultures drawn from the catheter and peripherally both grow Staphylococcus epidermidis. The catheter blood culture turns positive 2 hours before the peripheral culture. What criterion confirms catheter-related bloodstream infection (CRBSI)?
- A Differential time-to-positivity (DTP) ≥2 hours earlier for catheter blood culture compared to peripheral confirms CRBSI ✓
- B Identical organism in both cultures confirms CRBSI without requiring DTP
- C Any positive catheter blood culture regardless of peripheral culture constitutes CRBSI
- D Catheter tip culture with >10 CFU by sonication method is the only valid criterion
Explanation
Differential time-to-positivity (DTP): if the catheter-drawn blood culture turns positive ≥2 hours before the peripheral culture with the same organism, this confirms intraluminal catheter colonisation and CRBSI with high sensitivity (87%) and specificity (91%). This criterion allows catheter salvage (lock therapy in selected cases) without removal. Identical organism alone is insufficient as skin contaminant S. epidermidis may grow in both cultures coincidentally. Catheter tip culture (>15 CFU by roll-plate, or >100 CFU by sonication) is a retrospective criterion requiring catheter removal.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.