Beth Israel Deaconess Medical Center Laboratory Manual

Back to Specimen Collection
Back to Main Page of Lab Manual

• Assemble equipment, wash hands, and put on gloves.

NOTE:  Check all expiration dates of blood tubes/blood culture bottles before drawing blood.  Do not use expired tubes/blood culture bottles.  Discard all expired media appropriately, i.e., dispose glass containers in a sharps container.
• Select site and apply tourniquet.
• Vigorously scrub the skin over the planned venipuncture site in a circle approximately 8 cm (3 inches) in diameter with a sterile 70% isopropyl alcohol wipe and allow to air dry completely.
• Perform the skin scrub two additional times.
  

Inadequate preparation of the skin prior to a venipuncture for blood culture collection which results in growth of skin or environmental flora can increase the cost of intravenous antibiotics by 39% and the length of stay by 4 days (JAMA, 1991; 265:365-9). In this report, overall hospital charges for a contaminated blood culture were $4400 greater than costs for a patient with a true positive blood culture.

• Perform venipuncture (see "Instructions for Performing Venipuncture") and withdraw 20 ml of blood.
• Swab bottle septa (they are not sterile) with alcohol and allow to dry.
• Inject 8-10 ml (minimum acceptable: 3 ml) into 1 bottle and 8-10 ml (minimum acceptable: 3 ml) into the other bottle. Changing needles between bottles is not necessary. (When less than 20 ml of blood is available for culture, split the blood evenly between the two bottles.)

• No less than 2 and no more than 3 separate blood culture sets should be drawn in any 24 hour period. The yield from 3 blood cultures in a 24 hour period has been shown to be 99.9% for all types of bacteremia.
• Culture sets should be taken from separate venipuncture sites as soon as possible after the onset of fever or chills. Spacing the blood cultures during the 24 hour period may be helpful for documenting continuous bacteremia in patients with suspected endovascular infections, such as endocarditis.
• Always obtain at least 2 (and no more than 3) separate cultures prior to beginning antibiotic therapy.
• Wait at least 48 hours after obtaining the initial blood cultures before obtaining any additional ones.  If blood cultures are still negative after 48 hours and the patient’s clinical condition warrants it, draw two more blood cultures over the next 24 hours. Discussion with the Laboratory Director on-call to discuss other diagnostic strategies may be appropriate at this time.
• Current methods for culturing blood have been documented to be capable of detecting fastidious, slower growing organisms such as Viridans streptococci and HACEK group members (Haemophilus aphrophilus, Actinobacillus, Cardiobacterium, Eikenella and Kingella) within the routine 5 days of incubation. Therefore, extending incubation for blood cultures is of limited utility and is not generally done.  Note, however, that Brucella takes longer to grow and therefore, when Brucella is suspected, a Brucella blood culture must be specifically requested and will be held for 10 days.  When isolated, most Brucella cultures flag as positive within six days based on published experience with our blood culture system.  Brucella serological analysis should also be requested because of suboptimal sensitivity of culture.

• Prepare skin as described for routine blood cultures.
• Perform venipuncture and inoculate 3 to 5 ml of blood (5 ml maximum, 1 ml minimum) into Myco F/Lytic Bactec bottles. Do not inoculate more than 5 ml of blood.
• One or two samples per week are optimal for both fungemia and mycobacteremia detection.
• Note: yeasts (e.g., Candida) are generally detected using standard blood culture bottles.
• Blood cultures for Malassezia (e.g., in patients on total parenteral nutrition) should be sent in a Myco/F Lytic bottle with culture of this organism specially requested.  Furthermore, to optimize yield, blood should be drawn through the catheter used to administer TPN.
  

Bartonella blood cultures have extremely low yield, only a few have been isolated from blood across the world, none at BIDMC.  Prior antibiotic therapy precludes isolation.  Therefore, this test is no longer available at BIDMC.  Serology recommended instead.