A febrile patient has a central venous catheter in situ. Two peripheral blood culture sets and one set drawn through the catheter lumen are collected simultaneously. The catheter-drawn aerobic bottle flags positive at 10 hours and the paired peripheral bottle at 15 hours; both grow the same Staphylococcus aureus strain. What does this finding establish?

• A Catheter contamination, because the catheter bottle grew first
• B Nothing conclusive without catheter tip culture after removal
• C Peripheral skin flora contamination of both specimens
• D Catheter-related bloodstream infection ✓

Explanation

A differential time to positivity of the catheter-drawn bottle more than 120 minutes earlier than the paired peripheral bottle indicates a higher organism burden in the catheter lumen and is diagnostic of catheter-related bloodstream infection when the same organism grows from both. Contamination would show random or delayed growth patterns, and catheter tip semiquantitative culture is only an alternative method that requires line removal.

Reference: Mackie and McCartney Practical Medical Microbiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.