BLOOD CULTURE : COLLECTION

AIM

• To detect bacteremia • For the correct indication;• At the correct time; and • Using the correct technique in order to

prevent contamination of the sample and minimize risk to patients and staff.

A false positive blood culture is defined as growth of bacteria in the blood culture bottle that were not present in the patient’s bloodstream and were introduced during sample collection.

Contamination can come from a number of sources:

• the patient’s skin, • the equipment used to take the sample and

transfer it to the culture bottle, • the hands of the person taking the blood sample, • or the general environment

IMPACT OF TECHNIQUE

• Studies have demonstrated sources of contamination at every stage of the process of obtaining and processing blood cultures

• The consensus, however, is that the most common source of contamination is the process of phlebotomy and inoculation of blood culture bottles.

3 Simple Steps

• Skin Preparation

• Kit Preparation

• Sample collection

Skin disinfection

• The primary agents for skin disinfection are iodine compounds, alcohols & chlorhexidine

• The most important concept in skin disinfection is that bacteria do not die at the instant of contact with disinfectant agents.

Skin preparation

• Thoroughly cleanse the patient’s skin before venipuncture.

• Use soap and water to clean visibly soiled skin and then clean your own hands.

• Apply 10% povidone iodine or (preferably) 2% iodine solution or (ideally) 2% tincture of iodine in 70% alcohol, in centrifugal circles at the anticipated site of venipuncture to disinfect the patient’s skin and allow to dry.

Kit preparation

• Ideally, remove the plastic cover immediately before collecting the sample; the top of the bottle will be clean but not sterile.

• Disinfect the tops of the culture bottles with a 2% chlorhexidine in 70% isopropyl alcohol impregnated swab.

• Allow the alcohol to fully evaporate before proceeding with bottle inoculation.

Collection

• Fresh stab

• No lines to be used UNLESS CA-BSI is suspected (or no other access possible).

Volume

• The magnitude of bacteremia affects blood culture yield, especially when small blood volumes are used.

• The likelihood of growth is lower and the median time to detection is later when small volumes (<0.5 mL) are used, particularly at ultralow concentrations of bacteria

Age Group/Weight (kg)

Ideal Volume of Specimen per Set (mL)

Neonates   1–2

Infants (5–10)   2–4

Children (7–20)   3–8

Children > 20  10

Children > 40  20

Adults and children > 60  30

* Rule of thumb: 4 mL of blood per 10 kg weight.

Questions & Comments