108 LABORATORY BACTERIOLOGY 
EXERCISE XLVI 
AGGLUTINATION TEST FOR DIAGNOSIS 
163. This test depends upon the fact that when the blood 
serum of an individual suffering with certain infections such 
as typhoid or glanders, or that has recently recovered from 
such infection, is added to a bouillon culture of the organ- 
ism, the bacteria become less motile, in case of motile bac- 
teria, and soon agglutinate in small clumps. The dilutions 
used vary from equal parts of serum and culture to dilutions 
of 1 to 50,000. It is recommended that the stronger dilu- 
tions be used, i.e. those from 1:10 to 1: 1000. ‘The test has 
proved to be of much diagnostic value, especially in typhoid 
fever and glanders. For diagnosis of glanders the macroscopic 
method of determination is necessary. See Part I1—The 
Diagnosis of Glanders. 
On account of the accuracy of this reaction it is employed 
extensively in many laboratories for diagnosis. 
164. Work for this exercise. Take one loopful of a fresh 
bouillon culture of typhoid bacilli (which will be furnished) and 
place it on a cover glass, add one loopful of diluted blood 
serum from a typhoid patient, or the blood of an immune 
guinea pig, and immediately make a hanging-drop preparation 
with a loopful of the mixture and examine. Note the effect 
on the motility of the bacilli and their aggregation into clumps. 
Specify the time elapsing before the agglutination appears and 
the time required for the complete clumping. 
Make a similar examination of a culture to which 1 to ro 
blood serum has been added. 
Repeat the above test with the blood from animals affected 
with or immunized against B. suipestifer. 
Examine a dried specimen of blood for this reaction. Add 
a few drops of bouillon or water to the drop of dried blood on 
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