384 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



show alternate bands of stained and un- 

 stained material and in addition one or 

 more metachromatic granules which are 

 best shown by special stains. Non-mo- 

 tile. Gram-positive but not intensely so 

 in older cultures. 



Gelatin colonies : Slow development. 

 Very small, grayish, lobulate. 



Gelatin stab : Slight growth on surface 

 and scant growth in stab. No liquefac- 

 tion. 



Agar slant : Scant, grayish, granular, 

 translucent growth, with irregular mar- 

 gin. 



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 

 tellurite in the medium. 



Rough (R) colonj^ form: Flat, margin 

 is very irregular. Surface is pitted and 

 very uneven. Very little light reflected 

 from surface. Translucent when viewed 

 by transmitted light. Colonies about 

 1 to 5 mm in diameter. 



Intermediate colony forms : Several 

 colony forms are found in this group 

 since the term includes all forms be- 

 tween the pure S form and the pure R 

 form. Sr forms very nearly approach 

 the S colonies and the sR forms nearly 

 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 sur- 

 face 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 (Mor- 

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



Broth: Uniform turbidity produced 

 by S form, pellicle produced by SR 

 form, sediment 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 

 occasionally reddish (Hill, Sci., 17, 1903, 

 375). 



Indole is not formed. 



Nitrites are produced from nitrates. 



All strains form acid from glucose and 

 fructose; some strains also ferment galac- 

 tose, maltose, sucrose, dextrin and 

 glycerol. 



Does not hydrolyze urea (Merkel, 

 Cent. f. Bakt., I Abt., Grig., H7, 1941, 

 398). 



A highly poisonous exotoxin is pro- 

 duced in fluid media. This toxin repre- 

 sents the principal disease-producing 

 agency of the organism. Toxin produc- 

 tion may fail in otherwise typical 

 strains. 



A highly potent antitoxin can be pro- 

 duced by repeated injection of toxin into 

 experimental animals. The antitoxin 

 possesses both curative and protective 

 properties. 



Serological types : In a study of 250 

 strains of Corynebacterium diphtheriae 

 Murray (Jour. Path, and Bact., .^/, 1935, 

 439-45) was able to classify 228 strains 

 into 11 serological types and 22 strains 

 remained unclassified (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 types which 

 have been confirmed by other workers; 

 these are distinguishable by colony form 

 on McLeod's blood-tellurite medium, 

 they are antigenically different with sub- 

 types, 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 



