Line infection / catheter-related bloodstream infection

• Bloodstream infection that occurs in association with peripheral or central venous catheters that have been present >48 hours.
• May be clinically obvious e.g. erythema, purulence at site, or non-specific e.g. fevers/general unwellness without apparent source.
• Fevers or unwellness that coincide with use or flushing of the line are suspicious for CRBSI.

• One of the difficulties with diagnosing line infection, is that it is often caused by common skin commensal organisms (e.g. coagulase negative staphylococci), which are also common contaminants of blood cultures.
  • Differentiating between these two scenarios if a CoNS is grown is difficult.
  • If >1 blood culture grows the same CoNS, this points more towards line infection.

In patients with fevers and peripheral or central venous catheters in place for >48 hours:

• Collect 2-3 sets of blood cultures
  • Ideally, at least one of these sets should be from a peripheral vein.
  • Avoid sampling from existing peripheral cannulae (high contamination rate).
  • In patients with multilumen catheters, all lumens don’t necessarily need to be sampled, as long as 2-3 sets are taken in total.
    • The evidence is uncertain on this, but the sensitivity for diagnosing CRBSI is probably more to do with total number of sets taken, rather than number of lumens sampled.

• If there is purulence at the exit site of the catheter, take a swab for culture.

• Line infection is the commonest cause of Staphylococcus aureus bacteraemia in patients who have been in hospital or had lines in for >48 hours.
  • S. aureus bacteraemia in this situation should prompt careful consideration of the line being the source.
• For other organisms, in the absence of an alternative source, the more sets of blood cultures that are positive with the same organism, the more likely CRBSI is.
  • This is especially the case for common skin organisms e.g. CoNS, corynebacteria.
• If blood cultures drawn from the line are positive, but peripheral cultures are negative, it may be more suggestive of line or hub colonisation, rather than CRBSI.

Culture of line tips

• This is no longer a recommended practise, as it rarely adds useful additional information, and positive catheter cultures are not considered diagnostic of CRBSI.

Blood culture differential time to positivity (DTP)

• This is where the time to positivity between peripheral and line blood cultures, collected at the same time, are compared.
• If the line culture flags positive significantly sooner it is taken as evidence of CRBSI.
• The predictive value of this approach is uncertain, and may vary by organism, so is no longer recommended.