Intravenous catheter tip culture

Specimen:

After removal of the catheter under aseptic conditions, the distal 5 cm of the catheter should be cut with sterile scissors into a sterile container for transport to the laboratory.

Method:

The most widely used method involves rolling the tip across an agar plate in a standardised manner and counting the colonies present after incubation.

Application:

Diagnosis of intravascular catheter-related bacteraemia.

Interpretation:

Isolation of > 15 cfu (colonies) of the same organism as that isolated from a peripherally collected blood culture differentiates catheter-related bloodstream infection from non-catheter-related bacteraemia.

Catheter-related local infections are very uncommon and bacteraemia almost never occurs if < 15 cfu are present.

The positive predictive value of > 15 cfu varies depending on the criteria for microbiological testing (eg, on routine removal at the cessation of therapy versus on the occurrence of a new fever), the composition of the catheter and the identification of the organism isolated.

Reference:

Dooley DP et al. J Clin Microbiol. 1996; 34: 409-412.

Siegman-Igra Y et al. J Clin Microbiol. 1997; 35: 928-936.