STUDIES UPON AGGLUTINATION 63 



THE TIME FACTOR IN THE AGGLUTINATION TEST 



Afrglutination tests after various periods of time were carried 

 out with the colon-tyiihoid group, in relation to certain titres of 

 the serum. 



Bad. typhosinn showed the reaction quicker than the other 

 organisms, but the aggkitination reaction of most of the strains 

 was completed only after standing over night, instead of after 

 three hours. However, some strains showed almost complete 

 agglutination in three hours; others only a trace in this time. 

 Of course with strong seioim, agglutmation took place soon after 

 mixing with the bacterial suspension. 



With Bad. paratyphosum B, the results were of the same order, 

 but less rapid than with Bad. typhosrim. 



Bad. coli comes after Bad. parnlyphosum B, with regard to 

 the speed of the reaction. 



Bad. paratyphosum A, and Bad. dysenteriae show relatively 

 veiy slow agglutination; in most instances, the reaction was 

 definitely obtained only after standmg over night. 



However, the speed of the reaction varies with the strains of 

 bacilli ; some strains were always quickly agglutinated and others 

 more slowly. 



THE USE OF SEVERAL STRAINS FOR THE WIDAL TEST (TABLE 13) 



In the Widal test most bacteriologists use only one strain of 

 bacillus with the serum of the patient. This method does not 

 give reliable results. Ordinarily we use polyvalent immune 

 serum for the identification of a bacillus; for the same reason we 

 should use several strams in testing the serum of a patient. 



A serum agglutination reaction depends upon the organism 

 infecting the patient. If the serum agglutinates the stock cul- 

 ture, it indicates a close relationship between this organism and 

 the organism which infected the patient; a negative test indi- 

 cates distant or no relationship. 



In a case of typhoid fever (P. B. G. Hospital) the serum showed 

 positive agglutination for three strains (nos. 1, 4, 33), but negative 

 for three others (nos. 3, 7, 29), and doubtful for one more (no. 2j. 



