582 



ORDER IV. EUBACTERIALES 



Gelatin colonies: Slow development. Very 

 small, grayish, lobulate. 



Gelatin stab: Slight growth on surface 



and scant growth in stab. No liquefaction. 



Agar slant: Scant, grayish, granular, 



translucent growth, with irregular margin. 



Blood-tellurite media: Produces gray to 



black colonies. 



Colony forms: Smooth (S) colony form: 

 Round and umbonate or convex, with even 

 margin and smooth surface. Opaque when 

 viewed by transmitted light, glistening and 

 somewhat moist in appearance when viewed 

 by reflected light. Colonies about 1 to 3 mm 

 in diameter. Growth frequently slowed or 

 inhibited by the presence of potassium tel- 

 lurite in the medium. 



Rough (R) colony form: Flat, margin is 

 very irregular. Surface is pitted and very 

 uneven. Very little light reflected from sur- 

 face. Translucent when viewed by trans- 

 mitted light. Colonies about 1 to 5 mm in 

 diameter. 



Intermediate colony forms: Several col- 

 ony forms are found in this group since the 

 term includes all forms between the pure S 

 form and the pure R form. Sr forms very 

 nearlj' approach the S colonies and the sR 

 forms nearl}' approach the pure R forms. 

 The SR form shows properties distinct from 

 either the S or R forms. The colonies are 3 

 to 5 mm in diameter. The margin usually 

 shows indentations. The surface is raised 

 but not convex; it may be nearly level or 

 show a central elevation surrounded by a 

 concentric depression and elevation. 



Dwarf (D) colony form: Colonies very 

 small, about 0.2 mm or less in diameter. 

 Margin round and even. Surface convex. 



All of the above colony forms have been 

 isolated from cases of diphtheria (Morton, 

 Jour. Bact., ^0, 1940, 768 ff.). 



Broth: Uniform turbidity produced by S 

 form, pellicle produced by SR form, sedi- 

 ment produced by the R form. 



Litmus milk: Unchanged. 



Potato: No visible growth. 



Blood serum: Growth grayish to cream- 

 colored, moist, smooth, slightly raised, 

 margin entire. May be bright yellow or oc- 

 asionally reddish (Hill, Sci., 17, 1903, 375). 



Indole not produced. 



All strains produce acid from glucose and 



fructose; some strains also ferment galac- 

 tose, maltose, sucrose, dextrin and glycerol. 



Nitrites produced from nitrates. 



Does not hydrolyze urea (Merkel, Zent. 

 f. Bakt., I Abt., Orig., U7 , 1941, 398). 



A highly poisonous exotoxin is produced 

 in fluid media. This toxin represents the 

 principal disease-producing agency of the 

 organism. Toxin production may fail in 

 otherwise tj-pical strains. 



A highly potent antitoxin can be pro- 

 duced by repeated injection of toxin into 

 experimental animals. The antitoxin pos- 

 sesses both curative and protective proper- 

 ties. 



Serological types : In a study of 250 strains 

 of Corynebacterium diphtheriae, Murray 

 (Jour. Path, and Bact., 41, 1935, 439-45) 

 was able to classify 228 strains into 11 sero- 

 logical types, and 22 strains remained un- 

 classified (Morton, Bact. Rev., 4, 1940, 196). 



McLeod et al. (Jour. Path, and Bact., 34, 

 1931, 667; ibid., 36, 1933, 169; Lancet, 1, 

 1933, 293) describe three tj-pes which have 

 been confirmed by other workers; these are 

 distinguishable by colony form on McLeod's 

 blood-tellurite medium, they are antigeni- 

 cally different with subtypes, there is some 

 difference between their toxins (Etris, Jour. 

 Inf. Dis., 50, 1934, 220) and the severity of 

 disease is associated with the type. 



Corynebacterium diphtheriae type gravis 

 grows with dark gray, daisy-head colonies; 

 ferments dextrin, starch and glycogen; is 

 not hemolytic; has very few small metachro- 

 matic granules; forms a pellicle and a gran- 

 ular deposit, and there is an early reversal 

 of pH in broth. 



Corynebacterium diphtheriae type mitis 

 grows in convex, black, shiny, entire colo- 

 nies; no fermentation of starch and 

 glycogen, and it is variable with dextrin; 

 hemolytic; metachromatic granules are 

 prominent; diffuse turbidity, infrequent 

 pellicle, and there is a late reversal of pH 

 in broth. 



Corynebacterium diphtheriae type intenne- 

 dius produces a small, flat, umbonate colony 

 with a black center and slightly crenated 

 periphery; not hemolytic; barring of bacilli 

 is accentuated; there is no fermentation of 

 starch and glycogen, and it is variable with 

 dextrin ; forms no pellicle but a fine granular 



