APPEARANCE IN CULTURE 377 



material very similar to that formed in actinomycosis. The disease 

 occurs rarely in man. Some cases have been characterized by ab- 

 scesses about the rectum, where the primary lesions apparently fol- 

 lowed injury by fish bones. 



Appearance in Culture. Actinomyces bovis is anaerobic or micro- 

 aerophilic, difficult to isolate, fastidious in its nutritional require- 

 ments, and it must be transferred at intervals of ten days to a few 

 weeks if a strain is to be maintained in culture. For isolation in 

 culture a granule should be removed from pus promptly after its 

 collection and freed of as much extraneous material as possible by 

 rolling it across the bottom of a sterile Petri dish with a sterile needle. 

 It should then be transferred to a deep culture tube containing 

 melted agar, crushed with a sterile needle, and mixed with the agar. 

 Dilution cultures should then be made from the original tube and 

 the cultures incubated at 37° C. If preferred the material can be 

 streaked on the surface of an agar plate which is then incubated 

 anaerobically, with or without the addition of carbon dioxide. 



If the material to be cultured is heavily contaminated the granules 

 can be quickly washed in physiological salt solution before cultures 

 are made, but delay in planting the material and exposure to air 

 greatly decrease the viability of the fungus. 



A. bovis will not grow on Sabouraud agar. Veal infusion agar, 

 containing 1 per cent glucose and adjusted to pH 7.4 is probal)ly the 

 most satisfactory medium for primary isolation. If deep tubes are 

 used isolated colonies in the dilution tubes can be removed by means 

 of a sterile Pasteur pipet having an internal diameter of 1 to 2 mm. 

 and transferred to fresh agar in order to obtain a pure culture. 

 Chopped meat broth and Brewer's thioglycoUate semi-solid medium 

 containing dextrose are also good media for A. bovis cultivation but 

 purification of a mixed culture is rather difficult from these substrates. 



In a deep culture tube of veal infusion agar or chopped meat broth 

 the fungus grows in the form of a white or yellowish cuneiform 

 colony (Fig. 132). In most cases there is a zone of optimum growth 

 about 2 cm. below the surface of the agar. The colonies of A. bovis 

 in a mixed culture can usually be differentiated from the lens-shaped 

 colonies of cocci by examining with a hand lens. Broth medium is 

 not clouded. 



Microscopic examination reveals crooked, sometimes branching, 

 diphtheroid elements which result from the dissociation of the fragile 

 hyphae (Fig. 136). If a colony only 2 or 3 days old is examined it 

 is easier to demonstrate the hyphal character of the growth. The 

 hyphae are 0.5 to 1 micron in diameter and have a characteristic 



