36 BACTERIOLOGY FOR NURSES 



11. Conradi Drigalsky Medium. 



(a) Agar 20 gm.. (6) 130 gm. of Kubel and Tiemann's 



Sodium chloride . . 5 gm. litmus solution 



Peptone 20 gm. 10 c.c. of 1 to 1,000 solution 



Nutrose 10 gm. of crystal violet 



Liebig's Extract . . 4 gm. 15 gm. lactose 



Water 1000 c.c. 



The ingredients (a) should be thoroughly mixed and heated in 

 the autoclave to dissolve. The mixture should then be cooled to 

 below 60 C., cleared, sufficient sodium hydroxide solution added 

 to give a decided alkaline reaction to litmus, and then filtered. 

 Ingredients (6) are next added and the medium heated for 10 

 minutes in the Arnold in order to obtain a thorough mixing. It 

 should then be tubed and sterilized by the fractional method. 



This is one of the media used specially for the isolation of the 

 typhoid group of organisms; the principle being that while the 

 food supply is favorable to the typhoid and colon bacilli the growth 

 of other intestinal bacteria is inhibited by the antiseptic action 

 of the crystal violet. The difference between the colonies formed 

 by the colon bacilli and those formed by the typhoid bacilli is 

 readily seen in the plated medium. The B. coli colonies are dis- 

 tinctly red and non-transparent, while those of B. typhosus are 

 smaller, bluish violet in color and of a somewhat glassy appearance. 



12. Loeffler's Serum. Three parts of calf or sheep serum is 

 mixed with one part of nutrient broth (1) which has been made 

 neutral to litmus. One per cent dextrose is added and the medium 

 is tubed. In order to coagulate the serum the tubes are placed 

 in an inspissator in a slanting position, or an Arnold sterilizer may 

 be used if the outer cover is replaced by a cloth and the temper- 

 ature is allowed to rise very gradually to 80 C. After coagulation 

 the medium is sterilized by the fractional method. This medium 

 is especially suitable for the growth of the diphtheria bacillus ; it 

 is useful also for other organisms. 



13. Blood Agar. One c.c. of fresh or defibrinated blood is 

 added to about 6 c.c. of melted agar cooled to 42 C. to 45 C., 

 well mixed and either slanted in the tube or poured into a Petri 

 dish. The simplest method of preparation is to thoroughly cleanse 



