DIPHTHEROID ORGANISMS 25 



dextrose and maltose, but 1 in 19, and of the entire number of strains 

 more than half failed to ferment any sugars. Acid formation, there- 

 fore, is limited in its range, never exceeding 2 carbohydrates and show- 

 ing weak splitting action in general. 



CLASSIFICATION 



Classification from the cultural standpoint is difficult because of the 

 manifold variations which are observed. The resolution of all diph- 

 theroids into a few distinct "types" such as suggested by Morse is 

 possible only for a limited number of organisms from a limited number 

 of sources. Lehmann and Neumann classify "pseudodiphtheria" from 

 eye and nose as Coryneb. pseudodiphtheriticum and Coryneb. xerosis, 

 including diphtheroids from both sources under each heading. 



More recent work such as that of Plotz on typhus fever (C. typhi- 

 exanthematici) indicates that the diphtheroid group may possess patho- 

 genic species which are far removed from the type C. diphtheriae. The 

 organism described by Plotz and his co-workers is an obligate anaerobe 

 with characteristic serum reactions. Some diphtheroids might be 

 classified from the viewpoint of human and animal diseases, and par- 

 ticularly striking cultural characters such as oxygen requirement and 

 sugar fermentations. C. acnes is anaerobic and might very well go 

 into this group of anaerobes. Here also belong those "oxygen tension" 

 diphtheroids which are not anaerobic in the usual sense of the word, 

 but which grow beneath the surface in solid mediums. The property 

 of gelatin liquefaction, not hitherto recognized as a diphtheroid charac- 

 ter, suggests another subgroup. 



With these points in mind the following classification is offered.. 

 An effort has been made to group the species logically but it is evident 

 that relationships between different types do not always permit the 

 most desirable grouping. Certain characters were used as a basis for 

 arranging the distinct species under a chosen type. These will become 

 evident as the tabulation is studied. In the key given here, all of the 

 known diphtheroids have been reviewed and certain new species added. 



CLASSIFICATION CF DIPHTHEROIDS 



GROUP 1. Diphtheria. Type C. diphtheriae (Klebs-Loeffler). 

 Nonmotile, nonspo re forming, gram-positive, does not liquefy gelatin, 

 shows polar bodies in young cultures. Aerobic and grows between 19 

 and 42 C. Acid produced in dextrose, maltose and dextrin. Produces 



