628 THE ENTEROCOCCUS 



Guinea-pigs again are less susceptible than mice but they also die of 

 cachexia several weeks after being inoculated with an enterococcus the 

 virulence of which has been raised by passage through mice (Thiercelin). 

 According to Eosenthal lesions are found in the intestines of guinea-pigs 

 killed by intra- venous inoculation. 



The saprophytic enterococcus becomes virulent after passage through 

 animals (Thiercelin and Jouhaud). These observers inoculated a large dose 

 of a broth culture of the saprophyte beneath the skin of a rabbit : an abscess 

 formed at the site of inoculation and the enterococcus was found in the pus. 

 When this pus was inoculated into mice the latter died of septicaemia in 2 or 

 3 days : after a second passage the mice died in 24-48 hours. 



SECTION II. MORPHOLOGY AND BIOLOGICAL PROPERTIES. 

 1. Microscopical appearance. 



The enterococcus is highly pleomorphic. In normal stools it appears as 

 a diplococcus, the cocci being rounded, oval, or more or less lancet-shaped, 



very variable in size and rarely encapsulated ; 

 sometimes the two elements are arranged at 

 an angle to each other. Frequently the two 

 cocci in a diplococcus are of different shapes 

 and unequal in size, one rounded, the other 

 lancet-shaped. 



In pus, in the stools of cases of enteritis, 

 and in the blood of mice the appearance is 

 similar except that many of the cocci are 

 encapsulated and look like the pneumococcus. 

 Two diplococci arranged in a chain and also 

 sometimes diplo-bacilli may be found. 



In young cultures numerous diplococci, 

 tetrads and short chains are found ; in older 



FIG. 296. Enterococcus. Film from ,. . , , . , -, -, ,- 



an agar culture exhibiting the pieo- cultures the chains are longer and have the 

 foSifS)? SlekM' Carbol - blue - appearance of streptococci. Sometimes, and 



especially on agar, the cocci are elongated 

 and have a bacillary appearance. 



Staining reactions. The enterococcus is easily stained by the basic aniline 

 dyes. It is gram-positive. 



2. Cultural characteristics. 



Conditions of growth. The enterococcus grows at ordinary temperatures, 

 but best at 35-37 C. : it produces neither gas nor indol. Broth and agar 

 are very suitable media for its growth ; liquid serum is not a good medium. 



In artificial culture the enterococcus is indifferently aerobic. In the tissues 

 while living as a parasite it grows better under anaerobic conditions and is 

 sometimes strictly anaerobic : but this strict anaerobiosis is merely temporary 

 and after passage through broth in vacuo the organism grows aerobically 

 (Thiercelin, Rosenthal). 



Culture media. Broth. After incubating for 24 hours the broth is cloudy ; 

 later it becomes clear, a whitish mucous deposit falling to the bottom of the 

 tube. 



Blood-broth. There is a slight cloudiness at first, and then a mucous layer 

 containing numerous micro-organisms floats for a time in the liquid, but 



