A Reevaluation of the Use of Media for the Isolation of Pleuropneumonia-Like Organisms of Avian Origin

M XANY workers 3,3,6,7,9,12 have described the isolation of pleuropneumonia-like organisms (PPLO) from the respiratory tract of birds. Other workers14,'810'11 have presented and compared isolation techniques. However, all of these studies must be reevaluated in light of the findings presented by Adler, Fabricant, Yamamoto and Berg2. The latter workers demonstrated that there was a wide variation in characteristics among PPLO of avian origin and that this variation was a major problem not only in the isolation of PPLO, but also in the interpretation of their pathological significance. Although five different serological types of PPLO were encountered in this study, so far only two types seem to be widely distributed and present a significant problem. The first type, called So, is the standard antigen strain. This type is definitely pathogenic, makes a good antigen, and is characterized by a relatively slow growth rate in culture media. The second type, called C, is either non-pathogenic or weakly pathogenic, usually makes a poor antigen, and is characterized by a very rapid growth rate in culture media. These two types are completely unrelated serologically, there being no cross-agglutination between them.