132 BACTERIOLOGY OF MEAT AND MEAT PRODUCTS 



a number of diseases in pigs (as secondary invaders), rats, mice, 

 calves, birds, etc. 



The characters of B. enteritidis and the other true Gaertner 

 bacilli are briefly as follows : short bacilli with rounded ends, 

 not staining by Gram's method, actively motile, no spores. 

 They grow readily in broth with or without scum formation, 

 do not liquefy gelatine, on potato form a white or yellow-brown 

 growth. Indol is not produced. The growth in litmus milk is 

 somewhat distinctive as acid is first produced, the medium 

 becoming subsequently distinctly and often very markedly alka- 

 line. The sugar-alcohol fermentations are important, glucose, 

 dulcite, mannite, maltose, galactose and laevulose being fermented 

 with the production of acid and gas, while lactose, saccharose, 

 salicin, inulin and raffinose are not fermented, neither acid nor 

 gas being produced. With media containing glycerine a little 

 acid is produced with some strains but never gas. 



Of these varied cultural tests reliance is chiefly to be placed 

 upon the characteristic growth in litmus milk, the absence of 

 indol formation, the power to ferment dulcite and mannite, and 

 the failure to ferment lactose, saccharose and salicin. 



When recently isolated most Gaertner group strains possess 

 high virulence to rodents, causing gastro-intestinal symptoms, 

 general infection and death. These symptoms follow intra- 

 peritoneal or subcutaneous infection and frequently can be 

 induced, but with far less certainty, by feeding. All the varieties 

 of the group produce toxins which are remarkably heat resistant. 

 The bacilli themselves are fairly easily killed (i.e. 30 minutes at 

 60 C), but their toxins are capable of resisting heating to 

 1 00 C. for so long as thirty minutes. Under artificial culti- 

 vation outside the animal body the power to produce heat- 

 resisting toxins is rapidly lost. 



The above properties are shared by all the varieties included 

 under the true Gaertner group. The distinction between B. 

 enteritidis and the other two strains is readily made by aggluti- 

 nation tests. For example, the serum of an animal immunised by 

 the repeated injection of B. enteritidis in non-fatal doses aggluti- 

 nates highly and frequently to the maximum titre all strains of 

 B. enteritidis, whatever their origin, but with strains of B. 



