DYSENTERY AND ALLIED BACILLI 11 



SUMMARY AND CONCLUSIONS 



Observations made on 111 strains of dysentery and dysentery-like 

 organisms indicate: 



1. The strains of B. dysenteriae Y used in different laboratories are 

 not of the same serologic group. 



2. The main groups of the dysentery and closely allied bacilli, 

 B. dys. Shiga, B. flexneri, B. ambiguus, B. alkalescens and B. dispar, 

 are readily differentiated by fermentation reactions. B. dys. Sonne 

 appears to be intermediate between B. dispar and B. flexneri. 



3. Subdivision of B. flexneri on fermentation reactions is not advis- 

 able, but the flexneri Z race seems to be characterized by acid pro- 

 duction from rhamnose. This character is also strikingly correlated 

 with an inability to attack raffinose when sucrose is fermented. 



4. B. alkalescens and B. dispar form acid from glucose rapidly in 

 a medium containing 1.5% peptone, 0.4% dipotassium phosphate, and 

 0.2% glucose, then revert rapidly to an alkaline reaction. B. dys. 

 Shiga, B. flexneri and B. ambiguus form acid less rapidly -and remain 

 permanently acid or revert slowly. 



5. Dyes, such as eosin and methylene-blue, the fuchsin-sulphite 

 indicator, and excess of rosolic acid or china-blue were found to inhibit 

 many strains of dysentery, particularly the Shiga type. 



6. The following medium is suggested for isolation work : 



Distilled water 1,000 c c 



Agar 15 gm. 



Peptone 10 gm. 



Dipotassium phosphate 4 gm. 



To each 100 c c of the melted medium add before using: 



Lactose, 20% solution 5.0 c c 



Glucose, 5% solution 1.0 c c 



Rosolic acid (1.0% in 90% alcohol) '. . 1.0 c c 



China-blue (0.5% in water) 1.0 c c 



The H-ion concentration of this medium, which requires no adjust- 

 ment of reaction and does not need to be filtered when used on plates, 

 is 7.4 to 7.5. 



