378 ACTINOMYCES 



Resistance. — The members of this group show no special resistance to heat 

 or disinfectants. Most are killed in 15 minutes when exposed to moist heat at 

 60° C. Some attempts have been made to find whether filaments containing 

 so-called spores are specially resistant. Vincent (1894), working with Actinomyces 

 madurcB, stated that the spores were killed at 85° C. in 3 minutes, whereas the 

 non-sporing forms were killed at 60° C. in 3 to 5 minutes. 0rskov (1923) has 

 likewise found that the " spores " are more resistant than the plain mycelium ; 

 they may survive exposure to moist heat for 3 hours at 65° C. Goyal (1936), 

 however, was unable to show that the " spores " were any more resistant than 

 the filaments ; both were killed by a time-temperature combination varying with 

 different strains from 30 minutes at 60° C. to more than one hour at 72° C. There 

 is, of course, a great difference between the resistance of the Actinomyces " spores " 

 and that of true bacterial spores. 



Cultures of the aerobic type, if kept at room temperature, remain viable for 

 months ; cultures of the anaerobic type usually die out in about 6 to 8 weeks. 

 If kept in the incubator they die very much more quickly. 



Growth Requirements. — There is a fairly sharp division between the aerobic 

 and the anaerobic types. The aerobic types are unable to grow under strictly 

 anaerobic conditions, while the anaerobic types are unable to grow, at any rate 

 on solid media and when first isolated, in the presence of air. In liquid media, 

 especially in nitrate bro'th, and in the depths of solid media, such as glucose agar, 

 the anaerobic types may flourish when kept under aerobic conditions, showing that 

 they are not strict anaerobes, but rather organisms having a preference for a low 

 oxygen pressure — micro-aerophiles. Intermediate types are met with (Bruns 1899, 

 Lignieres and Spitz 1903), usually having a preference for anaerobic conditions 

 (Naeslund 1925). The development of both aerobic and anaerobic types is favoured 

 by the addition of 10 per cent. COj to the atmosphere. The range of temperature 

 over which the aerobic species are able to grow is very wide. Many of the water 

 and soil strains multiply even at 3-6° C, while nearly all strains grow between 

 6° and 30° C. About 30° C. some strains fail to grow, but the majority have their 

 optimum temperature round about 37° C. Thermophilic species are encountered 

 with an optimum temperature between 40° and 70° C. The anaerobic strains are 

 more fastidious in their requirements, and fail to grow if the temperature 

 varies more than a few degrees from the optimum of 37° C. (Lieske 1921). Growth 

 is improved as a rule by the addition of glucose or glycerol, sometimes by blood or 

 serum. 



Biochemical Characteristics. — The anaerobic type produces acid, but no gas, 

 in glucose, maltose, lactose, and sucrose ; strains of human origin (see ]). 379) 

 ferment also mannitol and salicin (Erikson 1940). Fermentation is often very 

 slow. The aerobic types have, as a rule, no action on these substances. Many 

 of the aerobic types turn litmus milk slightly alkaline and peptonize it slowly ; 

 the anaerobic type turns it acid (Negroni and Bonfiglioli 1937-38, Slack 1942). 

 A few members are proteolytic, digesting gelatin and serum, but the majority 

 have no proteolytic power. The anaerobic type cannot grow in the presence of 

 bile salts ; some of the aerobic types are able to do so. 



None of the strains that we have tested was heemolytic, but Waksman (1918) 

 has noted haemolysis in certain strains, and has correlated this property with the 

 power to digest proteins. 



