A patient with a central venous catheter develops fever on day 8 of ICU admission. Blood cultures drawn simultaneously from the catheter lumen and a peripheral vein both grow Candida tropicalis. Differential time to positivity (DTTP) shows the catheter bottle flagging positive 2 hours earlier than the peripheral bottle. What does this indicate?
- A Central line-associated bloodstream infection (CLABSI) with the catheter as the source ✓
- B Peripheral venepuncture contamination
- C Secondary bacteraemia from a distant focus (e.g., abdomen)
- D Indeterminate — DTTP is not applicable to Candida species
Explanation
Differential time to positivity (DTTP) ≥2 hours between paired catheter-drawn and peripheral blood cultures indicates that the catheter is the primary source of infection — the higher organism burden in the catheter blood flags the culture bottle positive earlier. This criterion has >90% specificity for CLABSI and avoids unnecessary catheter removal if DTTP is <2 hours. DTTP is validated for both bacterial and fungal CLABSI. Peripheral contamination would not produce the same organism in catheter blood. Abdominal source bacteraemia is possible but DTTP data supports catheter origin.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.