Chapter II 



35 



Important Types 



ing away all in one piece. The smooth colonies resemble those of white 

 staphylococci or diphtheroids. They are soft and easily broken and 

 emulsified. It was recognized, however, that on anaerobic-COj plates, 

 the colonies are very different from those found on aerobic media; an 

 occasional rough white colony may, on examination, turn out to be a 

 streptococcus. 



A summary of the morphological and cultural properties of the 

 pathogenic forms as compared to those of the saprophytes is given in 

 Table 3. 



Table 3: Comparison oj the parasitic and saprophytic actino7nycetes (367): 



Parasitic actinomycetes 



Saprophytic actinomycetes 



Natural 

 habitat- 



Cellular 

 morphology: 



Mouth and throat of man and 

 probably of cattle and other 

 animals; obligate parasites; 

 sometimes pathogenic. 



Branched mycelium, gram-posi- 

 tive, not acid-fast. Marked 

 tendency to fragment into bac- 

 illary forms. 



Soil, grains and grasses; widely 

 distributed in nature; some 

 pathogenic species, but most 

 forms are non-pathogenic. 



Branched mycelium, gram-posi- 

 tive; some are acid-fast. Gen- 

 erally little tendency to frag- 

 ment into bacillary forms. 



Character of Bacteria-like colonies without 



growth: aerial hyphae; no spores; no 



pigments. 



Temperature Optimum, 37°C.; no growth at 



requirements: 22°C. 



Relation to Oxygen tolerance limited; gener- 



oxygen: ally fail to grow or grow poorly 



under aerobic conditions. 

 Metabolism: Probably never proteolytic. Fer- 



ment carbohydrates with pro- 

 duction of acid. 

 Species One only: Actinomyces bovis. (Pro- 



recogni^ed: visional; heterogeneous but not 



yet satisfactorily subdivided.) 

 Pathogenicity: Causative agent of true actinomy- 

 cosis in man and animals. 



Colonies more mold-like, often 

 with aerial hyphae and spores 

 (conidia); many produce yel- 

 low, orange or black pigments. 



Optimum usually 15-20°C. 



Aerobic; some forms do not grow 

 anaerobically. 



Many forms actively proteolytic; 

 may utilize carbohydrates with- 

 out acid production. 



Many, subdivided into several 

 families. 



Occasional causes of an actinomy- 

 cosis-like disease, very rare in 

 man, and of tropical cutaneous 

 mycetomas, e.g., Madura dis- 



