BACILLUS FRAGILIS 573 



Experimental inoculation. Guinea-pigs appear to be the only laboratory 

 animals susceptible to infection with the bacillus. 



Morphology. -The Bacillus thetoides is a pleomorphic organism. In the 

 tissues, it generally occurs as a slender fairly straight rod : in cultures, rods, 

 filaments, and forms with terminal enlarge- 

 ments are found. It is non-motile. 



Staining reactions. The Bacillus thetoides Q f== ^ 



stains badly with the basic aniline dyes : por- 

 tions of the organism remain unstained and & 



particularly the ends so that the bacillus not 



uncommonly resembles the Greek letter 0. It g _ 



is gram-negative. <^ I <, fl 



Cultural characteristics. The Bacillus the- ft ^ 



toides is a strictly anaerobic organism and \ 



does not grow at temperatures below 22 C. / \ 



25 C. It produces no gas. 



It grows on agar at 22 C. but not on gelatin. &'S^S^^!!g 

 Agar appears to be the best medium : on this 

 medium the growth of the organism takes the form of small rounded homo- 

 geneous pale yellow almost punctiform colonies with regular margins. 



VI. BACILLUS FRAGILIS. 



This bacillus was isolated by Zuber and Veillon from some pus from a case 

 of appendicitis and it has since been frequently found in pus from gangrenous 

 conditions of the appendix (Veillon and Zuber, Grigorofi), in peri-urethral 

 infections (Cottet, Jungano), in pulmonary gangrene (Guillemot), in dental 

 caries (Monnier), etc. 



Experimental inoculation. The Bacillus fragilis is not very pathogenic for 

 laboratory animals. 



A gangrenous inflammation generally follows the sub-cutaneous inoculation 

 of the bacillus into a guinea-pig and the animal may die from 20-30 days 



later. The inoculation of large doses of cultures 

 *^! * into the veins of rabbits leads to death from 



** cachexia ; there is no multiplication of the or- 



** ganism. 



\ -* Morphology .The Bacillus fragilis is a small 



- ^ short non-motile organism with rounded ends 



* I "" jf sometimes having the appearance of a diplococcus : 



*"* ^. it is generally longer in culture than in the tissues. 



\ / ^ It does not form spores. 



9 f ' - Staining reactions. The Bacillus fragilis stains 



with some difficulty with the basic aniline dyes 

 containing a mordant, so that in stained films it 



FIG. 270. Bacillus fragilis. Film frequently has a granular appearance due to parts 

 f f uchsin a b x% h oo culture ' Carbo1 ' of the organism not having taken the stain. It 



is gram-negative. 



Cultural characteristics. The Bacillus fragilis is a strict anaerobe and 

 grows slowly and feebly with a disagreeable smell and the production of a 

 small quantity of gas. Cultures have very little vitality and die if kept in 

 the incubator for 6-8 days. 



Broth. The medium becomes cloudy about the third day. 



Gelatin. Small punctiform colonies appear in about 10 days to a fortnight. 



