738 Actinomycosis 



of fine threads. The colonies adhere closely to the culture-media 

 and are so firm that they crush with difficulty. If the surface be 

 scraped, spores and fine threads may be secured. If the mass be 

 crushed, branched filaments may be secured. The colonies become 

 confluent in the course of time, and a thick wrinkled membrane 

 is produced. The growth liquefies blood-serum. 



Gelatin. — ^In gelatin puncture cultures an arborescent growth 

 occurs and the gelatin is liquefied. 



Agar-agar. — Upon agar-agar, and, glycerin agar-agar the growth 

 is similar to that upon blood-serum. The agar-agar turns brown 

 as the culture ages. 



Bouillon.^In bouillon the growth occurs in the form of large 

 granules if allowed to stand quietly; of numerous small granules if 

 frequently shaken up. The granules are similar in structure to 

 those formied upon the dense media. The bouillon does not become 

 clouded. 



Potato. — ^Upon potato the growth resembles that upon blood- 

 serum, but is slower in developing. The color is reddish-yellow 

 and the white down early makes its appearance. 



Eggs. — -The organism can also be grown in raw eggs, into which it 

 is carefully introduced through a small opening made under aseptic 

 precautions. In the eggs long, branched mycelial threads are 

 formed. 



The characteristic rosettes so constantly found in the tissues are 

 never seen in, artificial cultures. 



Metabolisml^ There seems to be some difference of opinion as 

 to the oxygen requirement of actinomyces. Israel, Bostrom and 

 others state that it grows best when provided with a free oxygen 

 supply. Wright found it to grow best under anaerobic conditions. 



It does not ferment sugar, and does not evolve gas. It liquefies 

 gelatin and blood-serum but does not coagulate milk. Some strains 

 seem to produce a small quantity of orange-red pigment. 



A small amount of soluble toxin appears in culture-filtrates. 



Temperature. — In well established strains accustomed to sap- 

 rophytic life, growth progresses slowly but continuously at 2o°C. 

 (room temperature). Freshly isolated cultures just being started 

 will only grow at 37°C. Growth ceases at a point between 4S°C. 

 and 5o°C. Wright found the organism killed after an hour at 6o°C. 



Virulence.— When the actinomyces is grown upon artificial 

 media the virulence is retained for a considerable time. Different 

 strains show varying degrees of pathogenesis, some being almost 

 or quite non-pathogenic, others virulent. The difficulty of making 

 successful injections of the laboratory animals Umits our power to 

 accurately gauge the virulence. 



Pathogenesis. — -Actinomycosis is almost peculiar to bovine 

 animals, but sometimes occurs in hogs, horses, and other animals, 

 and rarely in human beings. The disease can with difficulty be 



