BIOLOGICAL PROPERTIES 425 



It forms acid and gas also in Isevulose, maltose, 1 galactose, mannite, dulcite, 

 sorbite and glycerin : but neither acid nor gas in raffinose, saccharose and 

 lactose. 



The paratyphoid A bacillus does not ferment carbohydrates so power- 

 fully as the paratyphoid B bacillus. 



(/:?) Neutral-red media. The paratyphoid A bacillus like the colon bacillus 

 reduces neutral-red, and in media containing the dye may give rise to a 

 greenish fluorescence, but the reaction is less marked than with the colon 

 bacillus and the Salmonella group. Fluorescence in neutral-red media is 

 however a very inconstant change ; the best medium for the reaction is agar 

 containing 1 per cent, of glucose and 1 c.c. per litre of a saturated aqueous 

 solution of neutral-red. 



(7) Endo's medium. On fuchsin-agar decolourized with sodium sulphite 

 the bacillus, like the typhoid bacillus, gives colourless colonies. 



(8) Caffeine media. According to Ducamp the paratyphoid A bacillus 

 will not grow in broth containing O5 per cent, of caffeine (vide B. para- 

 typhosus B}. 



() Malachite green media. Malachite green is decolourized by the para- 

 typhoid A bacillus (1 week) but more slowly than by the bacilli of the 

 Salmonella group (48 hours). 



(f) Vaccinated media. The paratyphoid A bacillus does not grow on 

 media which have already served for the growth of the typhoid, colon, 

 paratyphoid A or paratyphoid B bacilli. 



(r?) Indol. The paratyphoid A bacillus forms no indol in culture. 



2. Virulence. 



Sacquepee and Chevrel were able to increase the virulence of the bacillus 

 by passing it through a series of animals by sub-cutaneous inoculation. The 

 inoculation of O5 c.c. of a twenty-four-hour culture of the exalted virus in 

 broth was sufficient to kill guinea-pigs. 



The virulence is lost somewhat readily in culture. 



3. Toxin. 



The paratyphoid A bacillus produces a soluble toxin in culture media. 

 Cultures sterilized at 60 C. are pyogenic when inoculated beneath the skin 

 of guinea-pigs. Cultures of an exalted virus sterilized by heat or filtered 

 through porcelain kill guinea-pigs when inoculated sub-cutaneously in doses 

 of 3-10 c.c. 



4. Vaccination. 



Guinea-pigs and white rats can be easily vaccinated against the para- 

 typhoid A bacillus by inoculating them with attenuated or sterilized cultures. 

 From the experiments of Gushing and of Sacquepee and Chevrel it would 

 appear that animals immunized against the paratyphoid A bacillus are also 

 immunized but to a lesser degree against the typhoid bacillus (intervaccina- 

 tion or group immunization). The serum of immunized animals is distinctly 

 immunizing and bacteriolytic for paratyphoid A. 



Human vaccination. In man, vaccination with Wright's typhoid vaccine 

 affords no immunity against an infection with the paratyphoid A bacillus. 



Prophylactic vaccination of the human subject though suggested (Bain- 

 bridge, Leishman) has not yet been attempted. Certain preliminary 

 laboratory experiments have however been quite recently recorded by 

 Cummins and Gumming. 



1 The amount of gas formed out of maltose is always small whatever the organism. 



