448 A MANUAL OF BACTERIOLOGY 



probably includes the atypical dysentery bacilli, referred 

 to by some authors as " pseudo- " and " para- " dysentery 

 bacilli. 1 



Agglutination reaction. The agglutination reaction is 

 given by the blood of patients suffering from the bacillary 

 form of dysentery, but not by the amoebic form (unless a 

 double infection be present, which occasionally is the case). 

 Agglutination in Shiga infections commences between the 

 fifth and twelfth day of the disease. A non-dysentery 

 serum may agglutinate the Shiga bacillus up to a dilution 

 of 1 in 50, but agglutination in a dilution of 1 in 64 or over 

 may be considered to be diagnostic. In Flexner infec- 

 tions, no agglutination should be considered to be diag- 

 nostic in dilutions lower than 1 in 256. Not every case 

 of dysentery gives agglutination, which may occur only 

 with the particular strain causing the infection. 



Pathogenic action. The organism generally seems 

 limited to the bowel and its mucous membrane and rarely 

 gains access to the blood. No characteristic lesions are 

 produced in animals by administration of the dysentery 

 bacillus per os. In man, cultures given by the mouth are 

 stated to have induced a typical dysentery. Animals 

 such as rabbits, guinea-pigs and mice are very sensitive 

 to injections of living and killed cultures ; in fact, it is 

 very difficult to immunise animals against the organism. 

 Amounts of 0-1-0-2 mgrm. of an agar culture given intra- 

 venously or intraperitoneally are fatal to these animals. 

 The Shiga strain seems generally to be the more virulent 

 one. 



In man the organism is abundant in the bloody mucoid 

 discharge from the bowel, and occasionally may be 

 recovered from the blood. At an early stage it may be 

 isolated from the faeces by means of litmus lactose agar 

 plates, on which it forms small transparent blue colonies ; 



1 See Medical Science : Absts. and Reviews, i, 1919, p. 348. 



