CHAPTER 40 

 THE PLEUROPNEUMONIA GROUP OF ORGANISMS 



Tentative Definition. 



IVIicroscopically visible, extremely ijleomorphic organisms showing granules, 

 rings, coccoid forms, filaments and other bizarre forms. Some forms can pass 

 coarse bacterial filters. Size of smallest elements varies from about 125 to 250 m/i. 

 Non-motile. Stain poorly with ordinary bacterial stains, but well with Giemsa. 

 Gram-negative. Grow in nutrient media in absence of living tissue cells. Facul- 

 tative anaerobes. Form characteristic minute colonies on suitable solid media. 

 Parasitic species require a high concentration of animal protein in the medium. 

 Readily destroyed by heat. Apparently no special resistance to glycerol. Some 

 species are bile-soluble. Antigenic specificity is usual, but not complete. AbiUty 

 to give rise to inclusion bodies in tissues very doubtful. Considerable degree of 

 host specificity. Immunity following disease does not appear to be specially 

 lasting. 



Though the organism responsible for pleuropneumonia of cattle (see Chapter 84) 

 was recognized and cultivated by Nocard and Roux as long ago as 1898, it is only 

 within the past few years that a number of closely related organisms, some patho- 

 genic, some saprophytic, have been described, and that the importance of a large 

 group of organisms possessing unusual and distinctive properties has been realized. 

 The complex morphology of the pleuropneumonia organism was described by 

 Bordet (1910) and by Borrel and his colleagues (1910). The fact that Berkefeld 

 filtrates often proved infective afforded ground for the belief that it was a filtrable 

 virus. The more recent observations, however, of Barnard (1926), Smiles (1926), 

 0rskov (1927), Nowak (1929), Wroblewski (1931), Ledingham (1933), KUeneberger 

 (1934), Tang et al. (1935, 1936), Turner (1935), and Merling-Eisenberg (1935) 

 have rendered it probable that only the tiny granular or elementary forms, and 

 the plastic filamentous forms, are capable of passing through coarse filters. 



The second organism of this group was described by Bridre and Donatien 

 (1923, 1925), who isolated it from sheep infected with contagious agalactia (see 

 Chapter 84). In 1935 KUeneberger reported the occurrence in cultures of Strepto- 

 bacillus moniliformis {Actinomyces muris) of a pleuropneumonia-like organism, now 

 referred to as LI, living apparently in symbiosis with the bacillus. This discovery 

 formed the start of a fruitful series of investigations. By means of the technique 

 that KUeneberger described for their cultivation, she and numerous other workers 

 during the following years succeeded in isolating, mainly from rats and mice, a 

 number of different species of pleuropneumonia-like organisms. The' existence 

 of similar saprophytic organisms was demonstrated in sewage by Laidlaw and 

 Elford (1936), and confirmed by Seiffert (1937a, h). 



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