Quantity

Microbiology Specimen Collection

Blood Culture Specimens

General Considerations

Because of the seriousness of the misinformation resulting from contamination of blood cultures, it is essential that blood culture collection be performed aseptically with scrupulous adherence to proper procedure.

Quantity of blood to be drawn:

1. Due to the relatively low numbers of bacteria present in the blood during most adult bacteremias, the amount of blood drawn for each culture is critical. Based on numerous studies, it is strongly recommended that, ideally, 20ml of blood per SET (10ml per bottle) be drawn.
2. The Biomerieux BacT/Alert bottles are designed to give the appropriate blood-to-broth ratio, with 10ml of blood per bottle. Do not add more than 10ml of blood per bottle as this will exceed the optional blood-to-broth ratio.
3. The absolute minimum that should be considered for culture for adults is 5ml per bottle. However, the less blood drawn, the less chance of recovery of bacteria.
4. For children, the amount of blood drawn should be a function of the per cent of their total blood volume, which is weight dependent. Refer to table below.