VII48-8 MANUAL OF METHODS FOR PURE CULTURE STUDY 



animals (large rabbits and monkeys) use about 0.5 to 1.0 ml.; for 

 medium size animals (e.g., guinea pigs) use 0.1 to 0.25 ml.; and for 

 small animals, such as mice, use 0.02 to 0.03 ml. 



Cisternal 'puncture. The skin is shaved and sterilized at the base 

 of the skull over the cisterna magna. Withdraw as much fluid as is 

 to be injected and then introduce the material with a syringe and 

 needle, taking care not to injure nerve tissue. 



Intraspinal. Injection is made between the lumbar vertebrae into 

 the spinal canal after withdrawing an equivalent amount of fluid. 



Infracardial. Attempts to inject intracardially frequently fail 

 and numerous attempts are inadvisable. The animal should be 

 anaesthetized, the hair clipped over the cardiac region, the skin 

 shaved and disinfected. One should palpate for the point of maxi- 

 mum pulsation, insert a sharp needle (the size depending upon the 

 animal) and feel again for the heart with the needle. When it is 

 located, the heart beat will pulsate the needle and syringe. The 

 needle can be easily plunged into the heart. Its entrance will be 

 indicated by the appearance of blood in the syringe. The material 

 must be injected slowly. 



Recovery of Organisms from Blood Culture 



The following factors affect the accuracy of blood cultures: — 



Bacteremia. The isolation of bacteria from the blood of apparently 

 normal animals is not related to sepsis nor to the pathogenicity of the 

 organism. In localized infection, showers of organisms may be 

 thrown into the blood stream at irregular intervals, necessitating 

 repeated cultures to demonstrate them. The sequence of organisms 

 in the blood is related to the stage of the infection, the rise in tempera- 

 ture and the ingestion of food. In typhoid fever the organisms are 

 more likely to be present in the blood during the first week or 10 days, 

 but in many other infections the best time is during the rise in fever. 

 Organisms invade the blood stream when resistance is low. 



Contamination. It is particularly important to prevent contami- 

 nation when studying diseases of unknown etiology. The Keidel 

 blood culture tube is of distinct advantage although Feder (1937) 

 recommended a blood culture technic which he claimed had advan- 

 tages over the Keidel tube. A special apparatus with the advantages 

 of the Keidel tube and with facilities for subculturing was described 

 by McLeod and Bevan-Brown (1918). Recently, a "Vacutainer"* 

 appeared on the market. 



The skin should be shaved and treated with a disinfectant such as 

 mentioned for subcutaneous injections. The particular culture 

 medium depends on the organisms expected. The antibacterial 

 action of complement can be overcome by using the culture medium 

 of Kracke and Teasley (1930) (See Leaflet II, p. II44-IO) or by using 

 a large volume of culture medium such as 200 ml. of broth. The 

 smaller the amount of blood used the less chance of non-pathogenic 



*Becton, Dickinson & Co. 



