126 STUDY AND IDENTIFICATION OF BACTERIA 



The Shiga strains are apt to cause a paresis of the hind extremities of the injected 

 rabbit which may be followed by^ paralysis and death. At the Lister Institute 

 injections of a soluble toxin produced a serum of marked antitoxic power. Such a 

 dysentery serum, which is probably both antitoxic and antimicrobic, is of curative 

 value. Shiga immunized horses with polyvalent cultures and obtained a polyvalent 

 serum which has reduced the death rate about one-third. 



The dysentery bacillus is present in the milky white, leukocyte filled 

 blood flecked mucous stools during the first five or six days of the dis- 

 ease. By the tenth day it has probably disappeared. Lactose litmus 

 agar is the most satisfactory plating medium. The stool of the first 

 two days may give practically a pure culture. The staining of a smear 

 from the muco-purulent stool is rich in phagocytic cells, many of them 

 packed with Gram-negative bacilli. In all cultural respects the dysen- 

 tery bacillus resembles the typhoid, and the only practical method of 

 distinguishing these two organisms, other than by agglutination reac- 

 tions, is by the nonmotility or exceedingly slight motility of the dysen- 

 tery bacillus. 



The characteristic of nonmotility is of greatest differentiating value and the 

 reports of slight motility are probably from misinterpretation of molecular movement 

 as motility. The dysentery bacilli do not form those threads or whip-like filaments 

 so characteristic of typhoid cultures and are somewhat plumper. 



As a rule they occur singly or in pairs, and of rather oval or even coc- 

 coid shape and may stain bipolarly. The colonies are much like those 

 of typhoid. Type "Y" colonies often show indentation while the 

 Shiga types show round colonies. 



The dysentery bacillus is not found in the blood and hence is not eliminated in 

 the urine. It is found in mesenteric glands. In dysentery patients agglutination 

 phenomena do not show themselves until about the twelfth day from the onset. 

 Hence, this procedure is of no particular value in diagnosis. It is of value, however, 

 to identify an organism isolated from the stools at the commencement of the at- 

 tack, using serum from an immunized animal or a human convalescent for the 

 agglutination test. 



Butler has suggested taking serum from dysentery convalescents, noting the 

 strain involved, and preserving it by taking up with filter-paper as recommended 

 by Noguchi for the Wassermann haemolytic amboceptor. This I consider very 

 valuable as it is very difficult to immunize rabbits with a Shiga strain on account 

 of its great toxicity. Dean has reduced the toxicity of Shiga vaccines by treat- 

 ing with eusol. 



There seems to be very little agglutination power in the serum of convalescents 

 from Shiga strains. Flexner strains give agglutination, but early in convalescence 

 the serum is not apt to have a titre of more than i to 50. 



