424 THE PARATYPHOID A. BACILLUS 



The paratyphoid A bacillus has been recovered from the gall bladder after death 

 and during operations for gall stones or cholecystitis ; it has also been isolated once 

 from an abdominal abscess and once from an apparently healthy man. Bainbridge 

 states that it has been isolated from a case of acute enteritis. The organism has 

 never yet been recovered from other than human tissues. 



SECTION I. EXPERIMENTAL INOCULATION. 



All strains of the paratyphoid A bacillus are virulent for laboratory animals. 

 The inoculation of 4 c.c. of a broth culture sub-cutaneously is fatal to guinea- 

 pigs (Brion and Kayser) : in mice, inoculation produces a fatal disease 

 accompanied with symptoms of acute enteritis. 



Guinea-pigs and mice are easily infected with a fatal disease by feeding 

 them on cultures of the bacillus. 



SECTION II. MORPHOLOGY. 

 1. Microscopical appearance. 



The paratyphoid A bacillus is a short stout rod-shaped organism with 

 rounded ends often having the appearance of a cocco-bacillus : in old cultures 

 long filamentous forms are occasionally seen. It is very motile and is provided 

 with, from four to ten delicate flagella. Morphologically it is indistinguishable 

 from the other bacilli of the typhoid-colon group. 



Staining reactions. The paratyphoid A bacillus stains readily with the 

 ordinary basic aniline dyes and occasionally exhibits polar staining. The 

 bacillus is decolourized by Gram's method. 



2. Cultural characteristics. 



The paratyphoid A bacillus is a facultative aerobe and grows readily on 

 the ordinary media in a manner very like the typhoid bacillus. 



Broth. The medium is rendered cloudy and has a watered silk appearance. 



Gelatin. The colonies are iceberg-like, translucent and bluish : in stroke 

 culture the growth is thin and streaked with blue. The medium is not 

 liquefied. 



Potato. On potato the bacillus gives a barely visible glaze. 



Artichoke. Generally colourless : a green colour may be produced after 

 some time. 



Milk. Milk is not coagulated. 



Litmus milk. In litmus milk, acid is formed, the colour of the litmus 

 being changed to pink (p. 373) : the acidity is permanent. No clot is formed. 

 The 'permanent acidity without clot is peculiar to this member of the typhoid- 

 colon group. 



Litmus whey. A slight but permanent acidity indicated by the change 

 in colour of the litmus from amethyst to pink. 



SECTION III. BIOLOGICAL PROPERTIES. 



1. Biochemical reactions. 



(a) Fermentation of carbohydrates. The paratyphoid A bacillus produces 

 acid and gas in glucose but has no action (producing neither acid nor gas) 

 on lactose. The bacillus is thus easily differentiated from the typhoid bacillus 

 on the one hand and from the colon bacillus on the other. 



