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A minimum of10 ml of blood is taken through venipuncture and injected into two or more "blood bottles" with specific media for aerobic and anaerobic organisms. A common media used for anaerobes is thioglycollate broth.
The blood is collected using aseptic technique. This requires that both the tops of the culture bottles and the venipuncture site of the patient are cleaned prior to collection with swabs70%isopropyl alcohol.[2]
To maximise the diagnostic yield of blood cultures multiple sets of cultures (each set consisting of aerobic & anaerobic vials filled with3–10 mL) may be ordered by medical staff. A common protocol used in US hospitals includes the following:
· Set1 = L. antecubital fossa at0 minutes
· Set2 = R. antecubital fossa at30 minutes
· Set3 = L. or R. antecubital fossa at90 minutes
Ordering multiple sets of cultures increases the probability of discovering a pathogenic organism in the blood and reduces the probability of having a positive culture due to skin contaminants.
After inoculating the culture vials, advisably with new needles and not the ones used for venepuncture, they are sent to the clinical pathology microbiology department. Here the bottles are entered into a blood culture machine, which incubate the specimens at body temperature. The blood culture instrument reports positive blood cultures (cultures with bacteria present, thus indicating the patient is "bacteremic"). Most cultures are monitored for5 days after which negative vials are removed.
chokolate agar
