752 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



certain specific infectious diseases. The serum must be properly 

 diluted in order that the reaction may be of diagnostic value, because 

 undiluted, normal serum will cause a positive agglutination reaction 

 in most cases. 



The agglutination test is used as a practical aid chiefly in typhoid 

 fever in man and glanders in horses. The test may be conducted either 

 microscopically or macroscopically. In the microscopic method, the 

 diluted serum from the suspected case is placed under the microscope 

 with the live, specific organisms in hanging drop. In the macroscopic 

 method, the serum is added to an emulsion of the killed (heated) 

 bacteria in small test-tubes, and the resulting reaction detected with the 

 naked eye. 



The emulsion, suspension or "test fluid" for the typhoid agglutina- 

 tion test is prepared from a pure culture of B. typhosus. The organism 

 is grown for twenty-four hours upon agar at a temperature of 37. 

 The growth is then removed from the surface of the agar, placed in 

 sterile, physiologic salt solution and the organisms killed by heating on 

 a water bath at a temperature of 60 for one-half hour. The emulsion 

 is then roughly standardized by adding sufficient sterile, physiologic 

 salt solution to impart to the fluid the required degree of cloudiness, 

 when compared with control emulsions. To the suspension of dead 

 typhoid organisms or "test fluid" a preservative, usually formalin, 

 is added and the product is- distributed in properly labeled bottles. In 

 conducting the test, the suspected typhoid serum is placed in small 

 tubes, each containing i c.c. of the suspension fluid, in such propor- 

 tions that the serum is diluted i : 50, i : 100, and i : 200. A flocculent 

 precipitate of the dead organisms indicates a positive reaction. 



Suspension fluid for the glanders agglutination test is prepared in 

 practically the same manner as the typhoid test fluid. The glanders 

 organisms are grown on acid agar and the suspension fluid is usually 

 preserved by the addition of carbolic acid. In conducting the glanders 

 agglutination test, the suspected serum is usually placed in the follow- 

 ing dilutions: 1:200, 1:500, 1:800, 1:1200, and 1:1800. 



The agglutination reaction has been applied experimentally and 

 practically, with more or less success, in the diagnosis of Malta fever, 

 Asiatic cholera, bubonic plague, pneumonia, tuberculosis, contagious 

 abortion (bovine) and other infectious diseases. 



