Blood Cultures

Please note that avoiding blood culture contamination reduces harm to patients from unnecessary investigations and treatment. It also reduces laboratory work and hospitalisation costs.

Specimen types you should send

  • Venous or arterial blood samples (Collected by venepuncture or from intravenous or arterial catheter devices).
  • Send more than one blood culture set in patients with severe bacteraemia or sepsis before commencing empirical antibiotic therapy. If clinically permissible collect samples 10 - 20 mins apart.
  • It is critical to disinfect the skin before venepuncture. Similarly hubs of intravascular devices should be disinfected before sampling.
  • Most important is the minimum amount of blood used for inoculation. For adolescents and adults 10 - 20 mL of blood is the minimum volume per set (i.e. aerobic and anaerobic bottle) and 1 -2 mL for neonates and young children (use the paediatric blood culture bottle please).
  • Mycobacterial blood cultures (red Bactec bottle) are also available from the department.

A guide for collecting blood cultures:

  • severe septicaemia (meningitis, osteomyelitis, arthritis, pneumonia: 2 cultures before antibiotic therapy commences.
  • Infective endocarditis: 3 cultures before therapy commences, if antibiotic therapy for infective endocarditis is delayed for 24 hrs collect another 3 sets the next day.
  • Low grade intravascular infection: 3 sets within 24hrs best taken at the start of febrile episodes. Best taken before antibiotic therapy.
  • Febrile episodes: no more than 3 cultures over 24hrs. Bacteraemia may be present 1 hr before febrile episodes.
  • Fever of unknown origin: 4 - 6 sets over 48 hrs.

How to Collect the Sample

  • Collect serum or plasma blood samples by Venepuncture or by sampling intravenous catheters. Follow local guidelines for venepuncture and sampling from intravenous catheters.
  • Observe universal precautions to reduce any potential infection risks through needle stick injuries. Wear gloves when obtaining blood samples to protect yourself.

Labelling

  • Please ensure that the Pathology Sample Labelling Policy is followed 
  • The request form should indicate the test requested, and clinical information (e.g. "?Enteric fever after returning from 2 weeks in Mexico". "To start on iv cefotaxime." or "Purpuric rash, shock, ?meningococcaemia. To start cefotaxime" or "Fever of unknown origin. Not on antibiotic therapy").
  • It is essential to indicate if this is a high risk sample and indicate so with Danger of infection stickers.

Which Container does it go in?

This sample should be sent to us in Bactec blood culture bottles.

For adult blood cultures use a set of 2 culture bottles (anaerobic and aerobic) for each collected blood sample. Red BUFALO blood culture collecting packs available.

For paediatric blood cultures please use a single paediatric blood culture bottle.

Transport

  • The bottles can be sent via the air tube system (bottles for mycobacteria SHOULD NOT be sent via the air tube system).  
  • Transport to laboratory as soon as possible. NICE guidelines state <4 hours from collection to monitoring system.

    Reporting

    • Positive blood culture bottles will be reported to you electronically, followed by telephone notification when we can inform you about the presence of presence of potential organisms via a Gram stain.
    • During this phone call we will enquire about the clinical condition of the patient, antibiotics used and we will give advice on antibiotic therapy where appropriate.
    • In most cases positive blood cultures will be followed up with susceptibility and identification results the following day.
 

Page Reviewed: 10/04/17 | Updated by: Kevin Roberts