156 



MEDICAL BACTERIOLOGY 



Morphology. Pus or fluid discharging from an actinomycotic lesion shows 

 hard, brittle, irregular, pin-point-sized, yellowish and whitish granules. Place 

 one of these granules on a slide, in a drop of glycerin and crush it with a cover 

 glass. Microscopic examination will reveal rosette-like masses. The dense 

 centers of these are composed of interwoven filaments, and the outer zone of 

 club-shaped bodies arranged in ray form. Here and there, isolated clubs and 

 filaments are observed, occasionally a filament terminating in a club-shaped 

 body. The filaments vary in length from 5 to 15 /*, the clubs are about 25 to 

 10 M- The addition of a drop of 20 per cent, potassium hydrate, or a drop of 

 Gram's solution, makes them appear more distinctly. These granules are not 



FlG. 3O. ACTINOMYCES, SHOWING BRANCHING OF THE FILAMENTS. STAINED WITH FUCHSIN. 



(4 X eyepiece and >i2 oil immersion objective.) 



always present. Early in the disease, when resistance to infection is slight, the 

 pus may only contain filaments. The filaments are long and short and show 

 branching. 



They stain with all the usual anilin dyes and are Gram positive and are acid- 

 fast (to a lesser degree than tubercle bacilli), but are not alcohol-fast. 



Organisms removed from culture media appear differently. Young cultures 

 show fine, branching, non-septate filaments, some of which are very long. Older 

 cultures, that have developed aerial hyphae, show short, thick, straight rods; 

 some have aerial hyphae branching from them and these aerial hyphae terminate 

 in a row of round, irregular-sized conidia; club-shaped forms are not observed. 

 Cultures do not show rosette forms. Involution forms, somewhat similar to, 

 but larger, than involution forms of diphtheria bacilli, are observed in very 

 old cultures. 



Growth. Streptothrix actinomyces is equally adapted to aerobic and an- 

 aerobic cultivation. Growth occurs at temperatures between 2oC. and 5oC., 

 best at 37C. 



