Chapter 2 



The Genus Actinomyces 



The genus Actinomyces comprises anaero- 

 bic or microaerophilic organisms. They are 

 mostly pathogenic in nature. The pathogenic 

 forms are nonacid-fast, nonproteolytic, and 

 nondiastatic. These have been isolated from 

 granules in the pus of morbid tissues of a 

 human and animal disease known as actino- 

 mycosis. They produce no filterable stages 

 and show no serological reactions with other 

 genera. 



There are also on record observations con- 

 cerning the occurrence in various natural 

 substrates of nonpathogenic, mesophilic, 

 anaerobic actinomycetes that can with full 

 justification be included in this genus. Al- 

 though few of these have been sufficiently 

 .studied, one such species is included. The 

 saprophytic forms may be proteolytic, ac- 

 tively fermentative, and may possess marked 

 reducing properties. 



The natural relationship of this genus to 

 the other genera of the actinomycetes, based 

 primarily upon morphological and cytologi- 

 cal studies, has recently been examined by 

 Bisset (1959). 



< Jassilieatioii of the Genus Actinomyces 



I. Pathogenic tonus or forms isolated from 

 pal hogenic specimens. 



1. Colonies soft, smooth, uniform, not adher 

 ent to the medium. No aerial hvphae. 



a. Causative agent of certain animal dis- 

 eases. 



I. Actinomyces bovis 

 li. Isolated from human saliva and carious 

 teeth. 



8. Actinomyces odontolyticus 



2. Colonies tougher in texture and warted in 



appearance, adherent to medium. Aeria 



hvphae rare. 



a. Hvphae gram-positive and stain faintly 

 with hemotoxylin. Causative agent of 

 certain human diseases known as actino- 

 mycosis. 



6. Actinomyces israelii 

 a 1 . Related form. 



4. Actinomyces discofoliatus 



1). Hvphae in pus granules stain with basic 

 stains. Cause of actinomycosis in cats 

 and dogs. 



2. Actinomyces baudetii 

 II. Nonpathogenic forms. 



1. Occurs in human mouth. 



7. Actinomyces naeslundii 

 a. Related form. 



3. Actinomyces cellulitis 



2. Occurs in ground waters. 



5. Actinomyces hvidhanseni 



According to Thompson (1950), there arc 

 two distinct species of anaerobic organisms 

 that should be included in the genus Actino- 

 myces: A. hurls which is responsible for most 

 cases of lumpy jaw in cattle, and .1. israelii 

 which causes most of the typical infections 

 in man. This separation of the genus agrees 

 with the concepts of other investigators. 

 One strain of A. israelii was recovered from 

 a bovine source, and it was suggested that 

 some bovine infections may be due to ^4. 

 israelii. On the other hand, the work of Holm 

 (1951) and Lentze (1948) indicates that a 

 small number of human infections may be 

 due to A. bar is. 



Cummins and Harris (1958) fully sup- 

 ported the conclusions of Erikson (1940) 

 and Thompson (1950) that bovine and hu- 

 man strains of Actinomyces are distinct. On 



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