Hemoculture

HEMOCULTURE, a culture of microbes obtained from blood. For hemoculture, blood is sterilely drawn from the median vein with a syringe. The elbow bend is thoroughly washed with alcohol and ether or smeared with iodine, an Esmarh valve bandage, rubber tube, or simply a towel is applied to the forearm to obtain venous congestion, while the pulse on the radial artery must be clearly palpable. A sterile syringe needle is inserted into the swollen vein, the required amount of blood is drawn into the syringe, the tourniquet is released, the needle is removed, and the puncture site is clamped with cotton. From the syringe, the liquid blood is sterilely (flaming the stoppers, the edges of the test tubes) sown onto various nutrient media. Obtaining a culture from blood is not easy. Often only repeated sowings lead to a positive result. Blood is best taken at the height of fever or at its onset, but not during remissions. Usually, blood is sown on broth with the addition of bile, sugar, ascitic fluid, serum, and so on, or on agar. (For the production of anaerobic cultures, a special technique is applied—see Anaerobes.) The sowing is kept for up to six days due to the bactericidal properties of the blood, which inhibit the growth of microbes in the first days. Usually, 1 cubic cm of blood is sown on 100 cubic cm of broth to also weaken the bactericidal properties of the blood by a large dilution. (On the obtaining of H. from a corpse—see Corpse.)