468 CORYNEBACTERIVM 



Loeffler's serum for 24 hours at 37° C, is not unlike the bacillary form of C. diphtherice ; 

 the differences consist in a preponderance of barred or segmented forms over the granular 

 form, the infrequency of club forms, the relative infrequency and inconspicuousness of 

 metachromatic granules, though these are often present in small numbers, and the rela- 

 tively slight pleomorphism. The cells of this species retain the Gram stain more tenaciously 

 than those of C. diphtherice. 



Growth. — On Loeffler^s medium, or on agar, C. xerosis forms colonies which are 

 smaller than those of C. diphtherice or of C. hofmanni ; the margins may become irregular 

 after 48 to 72 hours, and the colonies tend to adhere firmly to the medium during the 

 later stages of growth. Broth remains clear, or shows a slight turbidity, while a granular 

 deposit forms at the bottom of the tube. No pellicle is formed. The general conditions 

 of growth, as regards temperature, oxygen pressure, etc., do not differ from those of the 

 type species. 



Biochemical Reactions. — C. xerosis produces acid in glucose, maltose and saccharose, 

 but not in dextrin or mannitol. It does not acidify litmus milk, does not produce indole, 

 and does not liquefy gelatin. Nitrates are reduced. It apparently forms no haemolysin. 



Antigenic Structitre. — The antigenic constituents of those strains of C. xerosis 

 which have been examined differ from those of C. diphtherice on the one hand, and from 

 C. hofmanni on the other. 



Pathogenicity. — There is no adequate evidence that C. xerosis is pathogenic. 



C. ovis 



(Synonym. C. pseudotuberculosis ovis.) 



The Preisz-Nocard bacillus (see Nocard 1889, Preisz 1894) was originally isolated from 

 pseudotuberculous lesions in sheep. Similar organisms have been isolated from ulcerative 

 lymphangitis of horses by many workers. It resembles the type species very closely in its 

 general morphology and behaviour. 



Morphology. — Films from young cultures on Loefflers medium show slender, clubbed 

 bacillary forms, granular or segmented, often with numerous metachromatic granules, 

 and exhibit a considerable degree of pleomorphism. The appearances are, in fact, indis- 

 tinguishable from those presented by certain strains or cultures of C. diphtherice. 



Growth. — The organism grows well on Loeffler''s medium, giving colonies which are 

 circular, umbonate, and opaque, with a tendency towards the development of a distinct 

 yellowish pigment. As they enlarge they often develop a series of concentric rings round 

 the raised centre. The growth is described as peculiarly friable, the colony breaking apart 

 when touched by the needle (Hall and Stone 1916). The growth on agar is recorded as 

 poor. Growth in broth is scanty, but there is definite pellicle formation. On blood agar, 

 especially under anaerobic conditions, colonies are surrounded by a zone of haemolysis. 

 Moderate granular growth in gelatin with sUght saccate liquefaction. Aerobic and facul- 

 tative anaerobe, growing best at about 37° C. 



Biochemical Reactions. — Forms acid from dextrose, maltose, and glycerol. Accord- 

 ing to most workers (Hall and Stone 1916, Minett 1922a, b, Andrewes et al. 1923) mamiitol, 

 lactose and sucrose are not fermented, but Carne (1939) in Australia reports that about 

 half of his 133 strams from sheep fermented these sugars. Dextrin may be weakly 

 acidified. Carne (1939) gives the following additional reactions for his strains : M.R. 

 weakly positive, V.P. negative, HgS formed by about half the strains. Gelatin is lique- 

 fied slowly and irregularly ; nitrates reduced by some but not by all strains ; indole 

 not formed. C. ovis produces a hsemolysin, active against sheep, horse and rabbit cor- 

 puscles ; according to Carne (1939) the hsemolysin is thermolabile, non-antigenic, unrelated 

 to the exotoxin, and is linked to the cells so that it cannot be obtained free in a filtrate. 



Antigenic Structure. — At present uninvestigated. 



