324 Microbes and You 



animal passage), the bacteria are killed by subjecting them to a 

 temperature of between 56 and 60° C. for from forty-five to sixty 

 minutes. Temperatures above 60° C. often destroy certain anti- 

 genic properties of the bacterin. Inactivation of the organisms 

 may also be brought about by the addition of chemicals, such as 

 formalin, or by exposing them to ultra-violet radiation or to super- 

 sonic vibrations. 



After adjusting the concentration of organisms with physio- 

 logical saline as a diluent, sterility checks are conducted to make 

 certain that neither aerobes nor anaerobes are alive in the bacterin 

 after the physical or the chemical treatment. Merthiolate in a 

 bacteriostatic concentration is frequently added to serve as a 

 preservative. 



Bacterins have proven valuable in prevention of typhoid fever 

 (Salmonella tijphosa), whooping cough (Hemophilus pertussis), 

 staphylococcus infections (Micrococcus pyogenes), and other dis- 

 eases. 



Autogenous Vaccines 



Chronic infections, including various skin pustules, boils, etc., 

 are sometimes treated by injecting killed suspensions of the organ- 

 isms causing the infection. Since the patient is the source of the 

 bacteria used in the preparation of the vaccine, the suspension 

 is called an autogenous vaccine (outo means self, and genie means 

 to create). An antigen made from organisms freshly isolated from 

 the patient for whom it is to be used, usually yields more satis- 

 factoiy results than a vaccine prepared from old stock laboratory 

 strains of the same species. Minor strain differences between 

 organisms spell the difference between an excellent or a mediocre 

 response in clearing up the infection. Antigens are highly specific, 

 as are antibodies, and the more specific treatment it is possible to 

 give the patient, the better, in general, are the results. 



B.C.G. Vaccine 



These letters are an abbreviation for Bacille Cahnette-Guerin, 

 in honor of the two French scientists who developed the particular 



