THE ORGANISM OF CONTAGIOUS BOVINE PLEURO- 

 PNEUMONIA AND RELATED ORGANISMS* 



INTRODUCTION 



The organism of bovine pleuropneumonia is similar in certain respects to 

 filterable viruses. Both in infected tissue and in cultures, small elements 

 are present which pass through filters that retain bacteria. The organism 

 is not stained well by the usual bacterial stains and can be made visible only 

 by using special methods. Bovine pleuropneumonia and other diseases 

 caused by similar organisms were originally attributed to filterable viruses. 

 These organisms are different from \'iruses in an important point; namely, 

 they grow on suital^le media in the absence of living host cells. The cul- 

 tures consist of pleomorphic elements, the nature of which has only slowly 

 become apparent. By the studies of Nowak (Ann. Inst. Past., 43, 1929, 

 1330), Turner (Jour. Path, and Bact., 4i, 1935, 1) and Klieneberger and 

 Smiles (Jour. Hyg., 4^, 1942, 110), it has been established that the pleo- 

 morphic forms are part of a reproductive cycle different from binary 

 fission. The small elements in the cultures swell up into large round forms 

 which reproduce the small elements within their membranes. The mor- 

 phology of the organism is further complicated by the fact that long branch- 

 ing filaments are present in freshly isolated bovine strains. These break up 

 into granules or parts of the filaments swell up into large round forms. In 

 the judgment of some investigators, these properties, in addition to un- 

 usual softness and fragility, exclude the organism of bovine pleuropneu- 

 monia and similar organisms from the order of true bacteria. Ledingham 

 (Jour. Path, and Bact., 37, 1933, 393) has classified them with the Actino- 

 myces. Later, Turner (Jour. Path, and Bact., 4i, 1935, 1) placed them in 

 an independent order, Borrelomycetales, while Sabin (Bact. Rev., 5, 1941, 

 58) has even placed them in an independent class, Paramycetes. 



The observations of the present author give support to the classification 

 of Buchanan (Jour. Bact., 3, 1918, 44) who placed the genus Asterococcus 

 Borrel et al. with the organism of bovine pleuropneumonia {Asterococcus 

 mycoides Borrel et al.) as type, together with the genus Haemophilus Win- 

 slow et al. in subtribe Haemophilinae Buchanan of the tribe Bacterieae 

 Trevisan emend. Buchanan. In many strains of the pleuropneumonia 



*Common names have been used through Supplement No. 3 (except for Astero- 

 coccus and A. rmjcoides) as the author believes that a more suitable nomenclature than 

 any thus far proposed should be developed when agreement is reached as to the nature 

 of these organisms. Specific names that have been proposed are given merely as a 

 matter of record. No new names have been introduced. 



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