Specimen collection details
Specimen collection document
- Specimen collection document 01-02-2011 (PDF 140 KB)
Blood culture collection: Reducing our contamination rate
Background
Skin flora, such as coagulase negative staphylococci (CoNS), are a potential cause of infection in certain neonatal and paediatric patients, but they are also common contaminants in blood cultures. This can lead to unnecessary investigations, treatment and costs for the patient. It has been previously estimated that up to 50% of CoNS in blood cultures are related to contamination. In addition, changes to surveillance definitions means that CoNS are no longer included in the monitoring of central line infections, unless the same organism is grown from two or more collections. We would therefore like to reduce our contamination rate as much as possible by optimizing collection practices.
What sort of blood culture do I need to take?
-
All patients should have an aerobic culture (in either a yellow or green bottle depending on blood volume)
-
Some patients also require an anaerobic culture:
-
Oncology patients
-
Suspected gastrointestinal, gynaecological or oral focus of infection and GI surgical patients
-
Short gut syndrome patients
-
Other specialised culture bottles are available from the microbiology laboratory ext 5688 on request
What colour bottle do I need?
|
Bottle top colour |
Culture type |
Blood volume |
|
Yellow |
Aerobic Paediatric |
0.5-4mL |
|
Green |
Aerobic Adult |
5-10mL |
|
Orange |
Anaerobic |
5-10mL |
|
Black |
Mycobacterial |
5-10mL |
|
Silver |
Mycoplasma |
3-5mL |
How can I maintain asepsis?
-
Use a sterile basic dressing pack for your equipment
-
Blood cultures should be taken using sterile gloves after hand hygiene with microshield gel
-
Disinfect skin with Chlorhexidine 0.5% in 70% alcohol
(in neonates use 1 % aqueous chlorhexidine) -
Apply skin antiseptic in circular motion outwards from insertion site; allow to dry and repeat application
What collection methods are acceptable?
-
Syringe and needle
-
Aspiration from hub of newly inserted cannula
-
Butterfly needle and syringe
-
Umbilical and central lines immediately after insertion
DO NOT take blood from old peripheral intravenous cannulas
How can I prevent contamination of my blood culture?
-
Use sterile gloves and avoid palpating vein after skin antisepsis
-
Swab blood culture bottle top after removing dust cap with alcohol swab and wait 30 seconds to dry
-
Innoculate blood culture bottle PRIOR to other blood tubes
What cultures should I take if I suspect line sepsis?
-
A culture from the central line AND
-
A peripheral blood culture
How many blood cultures should I take before starting antibiotics?
-
2 cultures are optimal
-
This is particularly important in patients with central venous access
-
In a septic patient, antibiotics should not be withheld pending subsequent cultures
How may blood cultures should I take in a febrile patient?
-
3 blood cultures have been shown to have 96% sensitivity in detecting bacteremia
-
No more than 4 blood cultures should be necessary
Prepared 12/5/2009 by Vanessa Clifford, Microbiology Registrar (pg 5735)
