CHAPTER XII. 



METHODS OF OBTAINING PURE CULTURES FROM PATHOLOGIC 

 MATERIAL AND OTHER SOURCES. 



AFTER the bacteriologist is in possession of various types of sterile 

 culture media he may undertake the preparation of pure cultures 

 from pathologic lesions due to pathogenic bacteria or from other 

 materials, such as milk, water, food, etc. In some cases this is a 

 very simple and easy task. For example, if an animal has a deep- 

 seated abscess which has not broken by ulceration and the bacterial 

 cause is to be determined the procedure would be as follows: Have 

 in readiness a number of culture tubes, some slides, a platinum loop, 

 an alcohol lamp, several knives, and what is required to sterilize the 

 skin. 



1. An assistant shaves and cleanses the skin with soap and water, 

 strong alcohol, solution of corrosive sublimate 1 to 500 to 1000. The 

 skin is then dried with sterile cotton and covered with the same 

 material. 



2. The knife is heated over an alcohol flame, unless it is kept in a 

 small portable instrument sterilizer. After the removal of the sterile 

 cotton an incision is made which opens up the abscess. 



3. In the meantime the one who is to obtain the pure culture has 

 prepared himself as follows: He holds two culture tubes in his left 

 hand. Their upper ends have previously been heated over the flame, 

 which destroyed all bacteria that may have collected externally on 

 the cotton. When everything is ready the cotton plugs are removed 

 by a rotary twist and held between the second and third or third and 

 fourth fingers of the left hand. The tubes must be held obliquely, 

 not vertical, because in this position bacteria from the air may fall 

 into them, nor horizontally, because the condensed water would then 

 run out. 



4. The platinum loop is heated over the flame, allowed to cool for 

 a few seconds, and dipped into the pus in the abscess cavity and 

 then introduced into the first tube. There it is dipped into the con- 

 densed water and rubbed over the slanting surface of the culture 

 medium. This procedure is called inoculating the culture tube. 



5. After the first tube has been inoculated the platinum loop is 

 again sterilized and a second tube is inoculated like the first one. 



6. The platinum loop is again sterilized and laid aside and the 

 right hand, now free, closes the two inoculated tubes with the cotton 

 plugs; these are again burned superficially over the flame (this is 

 called flamed) and set aside. 



