CHAPTER VI 

 BACTERIAL VACCINES 



Bacterial vaccines with few exceptions as noted are suspensions or solutions 

 of attenuated or dead bacteria, or bacterial products, in normal salt solution. 



Stock vaccines are those made from cultures kept in the laboratory. 



Autogenous vaccines are those made from cultures of the offending organism 

 or organisms obtained from the infected person and used in the treatment of 

 that patient. 



Polyvalent vaccines are those made from various strains of the same organ- 

 ism obtained from different sources. Mixed vaccines are those_containing two 

 or more different species of bacteria. 



Some vaccines are prepared, standardized, sterilized and administered by 

 special methods. In general, most vaccines are made from 24-hour-old cultures 

 on the surface of solid media. The medium used depends upon the require- 

 ments of the organism one desires to make the vaccine with. Those that grow 

 well on agar are planted on agar; those that grow best on blood-agar or ascitic 

 agar are planted on them. Young cultures are most desirable but if growth is 

 not apparent in 24 hours incubation is extended to 48 or occasionally 72 hours. 

 The bacteria are procured by pouring sterile normal salt solution on the media 

 and shaking or scraping until the bacteria are suspended in the salt solution. 



The salt solution suspension of bacteria is then poured into a sterile tube or 

 flask and shaken to break up clumps. 



The number of bacteria per cubic centimeter is estimated by mixing equal- 

 sized drops of blood and bacterial suspension on a glass slide, spreading in a 

 thin, even film, staining with any blood stain and examining under an oil im- 

 mersion lens. A satisfactory count can only be made, when the shaking of the 

 bacterial suspension has been sufficient to break up clumps and evenly distribute 

 the individual organisms; when the mixture of blood and bacterial suspension 

 has been done so rapidly that the film is spread before clotting occurs ; when the 

 film is thin enough to present fields containing bacteria and red cells not too 

 numerous to count when examined through the oil immersion lens. The bac- 

 teria and red cells are counted in each field until a total of 500 red cells has been 

 counted; the number of bacteria counted is totaled. Multiply the number of 

 bacteria counted by 10,000,000. This gives the number of bacteria in each 

 cubic centimeter of the vaccine. 



This computation is based on the fact that normal blood contains 5,000,000,- 

 ooo red cells per cubic centimeter. 



After the number of bacteria per cubic centimeter has been determined the 

 suspension of bacteria is further diluted by the addition of sterile normal salt 

 solution so as to bring the bacterial content to 1,000,000,000 per cubic 

 centimeter. 



