390 TYPHOID FEVER 



(c) From the Urine. — In typhoid fever the bacilli are present in at 

 least 25 per cent, of cases, especially late in the disease, probably 

 chiefly where there are groups of the organism in the kidney substance. 

 The organism can also be found in paratyphoid infections. For methods 

 of examining the urine, see pp. 50, 73. As has been stated, the b. coli is 

 a frequent cause of suppurations about the genito-urinary tract, and thus 

 often appears in the urine. The significance of its presence is greatest 

 when accompanied by cytological evidence of the co-existence of inflam- 

 matory conditions. 



The ultimate differentiation of the pathogenic varieties of the 

 coli-typhoid groups is effected by the study of their agglutination 

 reactions to stock sera prepared by means of typical cultures (see 

 below, p. 393). During the war, high-titre sera agglutinating 

 the various bacilli in 1 : 5000, or even higher, dilution, have 

 come into general use for differentiating organisms when isolated, 

 the sedimentation method being most convenient when dealing 

 with numerous organisms. 



The Agglutination Eeactions op the Coli-Typhoid Bacilli 

 and Their Relation to the Differentiation of 

 Strains. 



We have seen that all the members of the group produce 

 agglutinating sera during the infections they originate. The 

 specificity of the reaction in each case is sufficient to constitute 

 a basis on which a diagnosis of the condition originated may be 

 rested. It proceeds from the action of the infecting organism ; 

 thus a strain actually isolated from a patient frequently is agglutin- 

 ated by his serum. The reaction is in practice, however, usually 

 elicited by the use of strains isolated from previous cases. 



Technique. — There are a number of general points which here require 

 attention. All finer work on agglutination must be carried out by means 

 which ensure accurate measurement of the dilutions prepared, and further 

 a sedimentation method — interpreted either by naked-eye or low-power 

 microscopic examination — ought to be employed. We have already, in 

 dealing with the Widal reaction in typhoid fever, detailed some of the 

 precautions to be observed in obtaining the necessary cultures. In the 

 case of the b. typhosus it is easy from small, localised, clinically typical 

 outbreaks of the disease to isolate undoubted strains of the organism and 

 to select those which readily undergo agglutination. Most laboratories 

 are provided with such cultures which have been proved to be trust- 

 worthy by years of trial. The situation is different with the other 

 pathogenic members of the group, especially when, as under war condi- 

 tion, several different intestinal diseases are prevalent at the same time. 

 Under such circumstances a number of strains may be obtained which 

 differ in their capacities for being agglutinated — a preliminary difficulty 

 being that organisms freshly isolated off such media as MacConkey's agar 

 often must be subcultured daily on plain agar for some time before they 



