Specimen Requirements

Since media into which blood specimens are placed have been developed as enrichment broths to encourage the multiplication of even 1 bacterium, it follows that these media will enhance growth of any stray contaminating bacterium such as normal inhabitants of human skin.

• It is undesirable to draw blood through a vascular shunt or catheter, since these prosthetic devices may harbor colonizing bacteria that are not present in circulating blood of patient; and blood obtained through catheters or ports would yield false-positive results.
• It is also recommended to draw blood below an existing intravenous line, if possible, since blood above the line will be diluted with fluid being infused.
• If requested to draw blood cultures from indwelling catheter lines or if no venipuncture site is available, indicate on request form “line draw.”

Timing of cultures can be flexible; intervals of up to 1 hour are acceptable.  If the physician is waiting to start antibiotics, the sets can be drawn 5 minutes apart.  Select different sites for collection.   Draw blood 1 hour prior to expected fever/chills (usually mid-afternoon) as blood may be sterile by the time fever begins.

Preparation of Patient and Collection of Blood

Please refer to the phlebotomy procedure for the instructions to properly prepare and collect blood culture orders.

Minimum volume:   8-10mL for Aerobic and Anaerobic bottles and 3mL for the Pediatric bottles.

Specimen stability:  Please deliver blood culture bottles to the microbiology lab ASAP.