Corynebacterium diphtheriae

Abstract

The diphtherial species was found to exist in the S (smooth), SR (intermediate), R (rough) and D (dwarf) colony forms. Organisms from these 4 main colony forms could be identified readily as diphtheria bacilli on the basis of their tinctorial, cultural and serol. reactions and by their pathogenicity for guinea pigs. The G forms, as descr. by Hadley. were also encountered. Serial transfers in acid glycerol broth, aging of broth cultures and growth in the presence of LiCl were the chief methods of bringing about dissociation of the cultures. With these differences in colonial appearances on plain agar could be associated variations in stability in saline solns. of varying cones, of NaCl, differences in appearance of the growth on K tellurite chocolate agar and certain quantitative variations in such properties as fermentation reactions, toxi-genicity, hemolysis, resistance to aging, etc. Cell morphology was also influenced by the colony form but numerous environmental factors markedly influenced the cell morphology. Typical bacilli were changed to coccus forms by the presence in the culture medium of certain chemical ions or body fluids. The practical significance of both types of variation was mentioned. Photographs of the 4 main colony types were included.