360 THE DYSENTERY BACILLUS 



form acid in sorbite, imilin, salicin, and isodulcite. One strain of the Flexner 

 type apparently identical with the dysentery bacillus isolated by Strong 

 forms acid in dulcite and cane sugar (Morgan). 



[Hiss divided dysentery bacilli into four groups according to their fermentation 

 reactions. 



[The first or Shiga group ferments the monosaccharides and sometimes, after an 

 interval of several days, maltose. 



[The second group represented by Hiss' Y bacillus (isolated from dysenteric 

 diarrhoea in children due to milk and identical with the bacillus found in cases of 

 asylum dysentery by Kruse and others) ferments the monosaccharides and mannite. 

 Maltose and saccharose are sometimes also but with difficulty decomposed with the 

 formation of acid. 



[The third group consisting of Strong's Philippine bacillus ferments the mono- 

 saccharides, mannite and saccharose, occasionally also maltose. 



[The fourth or Flexner (Manilla) group decomposes the monosaccharides, mannite 

 maltose, saccharose and dextrin. 



[To these Shiga subsequently added a fifth group ; the characteristic of the 

 organisms comprising it being that they give first of all an acid reaction in mannite, 

 which subsequently changes to an alkaline reaction. 



[Aveline, Boycott and Macdonald find that the fermentative reactions of the 

 Flexner group towards maltose and cane sugar are variable. Thus, 24 cultures were 

 tested with the result shown 



CANE SUGAR. MALTOSE. 



Days incubated, - - - 1 7 14 28 1 7 14 28 



Number of cultures acid, - 0014 2 3 13 24 ] 



[In litmus milk the mannite -fermenting bacilli first produce a slight acidity 

 (1-3 days) and ultimately become alkaline (15 days). Strong's bacillus is 

 the only strain which forms acid and clot (Morgan).] 



Indol production. The Shiga bacillus produces no indol in culture. Bacilli 

 of the Flexner type vary, some strains produce indol, others do not. [Accord- 

 ing to Morgan the vast majority of the mannite-fermenting group form indol, 

 some more freely than others.] 



Growth in arsenical and carbolic broth. All dysentery bacilli grow in broth 

 containing carbolic acid (0'075 per cent.) or arsenious acid (O'l per cent.). 



Growth on vaccinated media. On agar which has already served for the 

 growth of the Shiga bacillus neither the Shiga bacillus nor the bacilli of the 

 Flexner type will grow : the typhoid bacillus gives a very poor growth, the 

 colon bacillus on the other hand grows abundantly. 



Similar results are obtained with agar which has served for the growth of 

 bacilli of the Flexner type. 



On media which have served for the growth of the typhoid or colon bacillus 

 neither the Shiga bacillus nor bacilli of the Flexner type grow. 



2. Vitality. 



The dysentery bacillus is a somewhat delicate organism. In culture it 

 does not live for more than 3 or 4 weeks : in infected stools it appears to be 

 quickly destroyed by the other micro-organisms present, and especially by 

 the action of the colon bacillus, so that it cannot be isolated after 48 hours. 

 Direct sunlight and desiccation rapidly destroy the bacillus : it is killed in 

 less than an hour at 58 C. : and in sterile spring water at 20 C. it does not 

 live more than 8-10 days. In water containing saprophytic organisms the 

 larger the number of such organisms the more quickly does the dysentery 

 bacillus disappear, and at the ordinary temperature it cannot be recovered 

 after 2-10 days (Vincent) ; the higher the temperature also the more rapidly 

 does the organism vanish : this may [partly] explain the frequency of 

 epidemic dysentery in cold and temperate climates (Vincent). 



