662 PATHOGENIC MICROORGANISMS 



presents considerable technical difficulties and gives way to the no 

 less accurate and much simpler method of agglutination. 



Agglutinins. Agglutinins are formed in animals and man inoculated 

 with typhoid bacilli, and in the course of typhoid fever. It was, in fact, 

 while studying the typhoid bacillus that the agglutinins were first dis- 

 covered by Gruber and Durham. 



In animals, by careful immunization, specific typhoid agglutinins 

 may easily be produced in sufficient quantity to be active in dilution 

 of 1 : 10,000, and occasionally even 1 : 50,000 or over. In the blood 

 of typhoid patients, the agglutinins may often be found in dilutions. of 

 1 : 100 and over. It is interesting to note that irrespective of the 

 agglutinin contents of any given serum, there may occasionally be noted 

 differences in the agglutinability of various typhoid cultures, a point 

 which is practically important in the choice of a typhoid culture for 

 routine diagnosis work. Weeny 59 has called attention to the fact that 

 bacilli which do not readily agglutinate when directly cultivated from 

 the body, may often be rendered more sensitive to this reaction by sev- 

 eral generations of cultivation upon artificial media. Walker has 

 noted 60 a loss of agglutinability if the bacilli are cultivated in immune 

 serum. A similar alteration in the agglutinability of typhoid bacilli 

 was noted by Eisenberg and Volk 61 when they subjected the micro- 

 organism to moderate heat or to weak acids such as ^ HC1. 



Morishima 62 has recently studied the same phenomenon, and has 

 confirmed the observations of Eisenberg and Volk, 63 and others. He 

 has also shown, however, that if organisms are cultivated in anti-serum 

 for a sufficiently long time, their preliminary inagglutinability will 

 eventually, after twenty to seventy-five days, revert to almost normal 

 agglutinability . 



Practical application of agglutination to bacteriological work is 

 found in the identification of suspected typhoid bacilli, and in the 

 diagnosis of typhoid fever. 



When it is desired to determine whether or not a given bacillus 

 is a typhoid bacillus, mixtures may be made of young broth cultures, 

 or preferably of emulsions of young agar cultures in salt solution, 

 with dilutions of immune serum. The tests are made microscopically 

 in the hanging-drop preparation or, preferably, macroscopically in 



69 Weeny, Brit. Med. Jour., 1889. 



60 Walker, Jour, of Path, and Bad., 1892; Totxtikn, Holt. f. HyR., xlv, 1903. 



01 Eixenberg und Volk, Zeit., f. Hyg., xlv, 190:5. 



^Morishima, Jour, of Baeter., March, 1921. 



63 Eisenberg and Volk, Erbeg. der Immunit. Exper. Ther. Bakt. u. Hyg., 1913, 73. 



