CHAPTER 14 

 ACTINOMYCES AND ACTINOBACILLUS 



ACTINOMYCES 



Definition. Actinomyces, Harz 1877. 



Organisms growing in the form of a much-branched mycelium, which may break 

 up into segments or produce " spores." Aerial mycelium often formed under 

 suitable conditions. Mainly aerobic, but may be microaerophilic or anaerobic. 

 Usually saprophj^ic, but some species are parasitic on plants or animals, and may 

 give rise to disease. In animal body organisms are frequently arranged in colonies 

 composed of radiating threads with clubbed ends. Non-motile. Some species are 

 acid-fast. The type species is Actinomyces bovis Harz. 



The term Actinomyces bovis was originally given by Harz to a mould-like organism 

 which was found by Bollinger (1877) in the lesions of cattle sufiering from a 

 peculiar disease of the tongue and jaw, now known as Actinomycosis. This 

 organism was first cultivated by WolfE and Israel in 1891 under anaerobic con- 

 ditions. An aerobic organism, which is occasionally present in actinomycotic 

 lesions, but which is probably not eetiologically related to the disease, was isolated 

 in the same year by Bostroem (1891). In order to avoid confusion with the 

 anaerobic pathogenic type, we have suggested that Bostroem's organism should be 

 called Actinomyces graminis. Since then a number of similar organisms have 

 been isolated from a variety of diseases in man and animals, and from such situa- 

 tions as soil, grains, and grasses. 



These organisms appear morphologically as jointed or unjointed filaments, 

 which frequently show true branching. In culture, rod forms are not uncommon. 

 In the animal body, many of the pathogenic species are characterized by the 

 formation of granules of varying size, which are found to consist of a filamentous 

 mycelium surrounded by radiating clubs — a picture which is responsible for the 

 term " ray-fungus." (Botanically the term " ray " refers to the marginal portion 

 of a composite flower, consisting of ligulate florets arranged radially.) In their 

 staining reactions some species are acid-fast, though the majority are non-acid-fast. 

 It is evident that these organisms bear some resemblance to those of Mycohacteritim, 

 and in the classification furnished by the American Committee of Bacteriologists 

 in 1917 (Report 1917), Actinomyces and Mycobacterium were included in a single 

 family, known as the Mycobacteriacece. In the 1920 report (Report 1920), 

 however, it was decided to create a separate family of Actinomycetacece, which 

 should contain the genera Actinobacillus, Leptothrix, Actinomyces, and Erysipelothrix. 

 For descriptive purposes it is convenient to consider these genera separately, and 

 in the present chapter we shall confine ourselves to a description of Actinomyces 

 and Actinobcwillus. 



373 



