BACILLUS DIPHTHERIA 



211 



constricting line of division and are, for this reason, frequently found 

 in groups of\parallel rows. These groups somewhat resemble palli- 

 sades, and, hence, a pallisade arrangement of the diphtheria bacilli 

 from pure cultures is spoken of. The bacillus does not form spores and 

 is not motile. 



Cultural and Staining Properties. The diphtheria bacillus or Klebs- 

 Loeffler 1 bacillus is best stained with Loeffler's alkaline methylene 

 blue. When derived from a young blood-serum culture (eighteen to 

 twenty-fours hours' incubation) it generally shows very typical staining 

 properties. It does not take the dye uniformly, so that stained spaces 

 alternate with unstained spaces. The stain is generally taken at 

 either end and by a segment in the middle. This causes diphtheria 

 bacilli frequently to appear to the beginner like short chains of strepto- 

 cocci, but a more careful examination will show them to be unequally 



FIG. 116 



FIG. 117 



Pseudodiphtheria bacilli. (Park.) 



One of the very characteristic forms of 

 diphtheria bacilli from blood-serum cul- 

 tures, showing clubbed ends and irreg- 

 ular stain. X 1100 diameters. Stain, 

 methylene blue. (Park.) 



stained bacilli. When grown on agar they do not show this typical 

 behavior, but become much shorter and stain more uniformly, resem- 

 bling then more closely the non-pathogenic bacillus known as the 

 pseudodiphtheria bacillus. On this account Loeffler's blood-serum 

 mixture 2 should always be used in making cultural inoculations from 

 suspected diphtheria cases. The Bacillus diphtheria? retains Gram's 

 stain. It also grows on agar, on bouillon, and in milk. A twenty-four 

 hour culture on blood-serum mixture or agar shows comparatively 

 small, grayish- white, granular, moderately dry or slightly moist colonies. 

 The bacillus grows in the presence or absence of oxygen, best at 

 blood temperature. It does not liquefy gelatin and does not grow well 

 on it. It forms gas in the presence of glucose. Pure cultures are 

 generally obtained by first inoculating the blood-serum mixture, 



1 Named Klebs-Loeffler, after its discoverers. 



2 The formula for Loeffler's blood-serum mixture is given on p. 133. 



