376 



ACTINOMYCES 



organisms such as tubercle bacilli and staphylococci. Even dead tubercle bacilli 

 are said to stimulate their production. 



In sections of tissues the filaments may be difierentiated from the clubs 

 by a modified Ziehl-Neelsen stain. If a section is stained with carbol-fuchsin, 

 decolorized for 20 to 30 seconds with 1 per cent. H2SO4, and counterstained 

 with methylene blue, the clubs appear red and the filaments blue. 



The aerobic types, when growing in the animal body, generally form a tangled 

 mycelium without evidence of ray or of club formation ; but exceptions do occur, 

 as with Actinomyces madurce, which forms definite granules similar to those of the 

 WolS-Israel type. 



The most striking feature of the Actinomyces is their pleomorphism. All forms 

 may be seen — filaments, rods, cocci, and even spirilla. In the anaerobic type rod 

 forms predominate in culture, in Actinomijces madurcB filaments. But in most of 

 the aerobic types all forms are seen, coexisting in a single culture. For a detailed 



Fig. 60. — Actinomyces graminis. 



Colonies on agar plate, 7 days, 37° C. aero- 

 bically : X 8. 



Fig. 61. — Actinomyces bovis. 



Colony on agar plate, 14 days, 37° C. anaero- 

 bically : X 8. 



description of their morphology, the reader is referred to a monograph by Lieske 

 (1921). 



Cultural Reactions. — In general, growth on artificial media is readily obtained. 

 The usual media suffice, but the addition of glucose or glycerol is beneficial. The 

 aerobic types, with a few exceptions, multiply rapidly, so that in 24 hours definite 

 evidence of growth is visible on agar. The anaerobic types, on the other hand, 

 grow more slowly, taking 3 or 4 days to form macroscopic colonies. Great diversity 

 of cultural appearance is noticeable, particularly in the aerobic species. The 

 descriptions that follow refer only to some of the commoner types. 



On an agar plate the aerobic types form round, low convex, opaque, finely 

 granular colonies, which later undergo differentiation into a raised, knob-like, 

 sometimes radially striated centre and an effuse, ground-glass-like periphery. The 

 surface is finely granular and often has a " chalk powder " covering due to the 

 formation of aerial spores ; the edge is rhizoid, indented, or feathery (Fig. 60). 

 Most strains form pigment — yellowish, pink, or orange in colour— which becomes 

 apparent after a few days' incubation, and which may show progressive alterations 

 in tint. This is especially noticeable in cultures that have been incubated at 37° C, 



