CHAPTER XXIX. 

 BLOOD CULTURES AND BLOOD PARASITES. 



CLINICALLY, the most important examinations of the blood for 

 parasites is for the presence of various bacterial infections and for 

 certain blood protozoa and also filarial embryos. 



The modern method of culturing blood, especially for the detection of typhoid 

 or paratyphoid bacilli, is by the use of the bile media of Conradi. Test-tubes are 

 filled with 7 to 10 c.c. of i% peptone ox bile, or ox bile alone, and the medium is 

 sterilized in the autoclave. It is good practice to place the syringe in a plugged 

 test-tube containing salt solution, with the needle unscrewed. After autoclaving, 

 the sterile syringe can be taken to the bedside in the test-tube. Using a wide test- 

 tube, a forceps can be sterilized at the same time and used to attach the needle to the 

 barrel of the syringe. 



By using a piece of glass tubing into which the needle is inserted we may sterilize 

 the syringe easily in the test-tube. The glass tubing prevents the steel needle from 

 coming in contact with the glass of the test-tube and so prevents cracking the test- 

 tube. Instead of a syringe a better apparatus is a test-tube or an Erlenmeyer flask 

 \yith a double perforation stopper for insertion of two pieces of glass tubing, one 

 joined to a piece of rubber tubing carrying the needle and the other attached to a 

 rubber tube for suction by the operator's mouth. See Fig. 7. 



The skin should be scrubbed gently with green-soap solution and water for about 

 three minutes. The skin of the area to be punctured should then be sterilized by 

 the gentle application of Harrington's solution (not scrubbed) for one-half minute, 

 and should then be washed with sterile water. It appears to be safe to simply 

 scrub the area with 70% alcohol for one or two minutes. Applications of pure 

 carbolic acid on a gauze wad for a few seconds followed by neutralization with 70% 

 alcohol gives satisfactory sterilization. The present method of sterilizing skin 

 for taking blood or inoculating vaccines is simply to smear the site of entrance for 

 the needle rather heavily with tincture of iodine. A tourniquet is now applied to 

 distend the vein, and the needle is inserted in the direction of the venous flow. 

 Withdrawing 5 to 10 c.c. of blood, we loosen the tourniquet, (otherwise the blood 

 may flow from the puncture) then withdraw the needle, and force out abo'ut 1/2 c.c. 

 into the first bile tube, about i c.c. into the second, and 2 or 3 c.c. into the third. 

 It is well to reserve some of the blood for Widal tests. 



The bile tubes are now incubated for ten to twelve hours and then transfers 

 are made to bouillon tubes. These bouillon tubes can be used in six to eight hours 

 for testing the organism against known typhoid or paratyphoid sera. Test-tubes 

 containing 10 c.c. of ordinary bouillon with i% of sodium citrate are as satisfactory 

 as bile media. 



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