PLEUROPNEUMONIA GROUP

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1 THE FILTRABLE MICROORGANISMS OF THE PLEUROPNEUMONIA GROUP (APPENDIX TO SECTION ON CLASSIFICATION AND NOMENCLATURE) ALBERT B. SABIN From The Children's Hospital Research Foundation and the Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio The publication (1941) of my suggestions for the classification and nomenclature of the filtrable micro6rganisms of the pleuropneumonia group has brought forth a number of important comments. It may be desirable, therefore, to extend the original discussion because many points have been raised which may ultimately have to be considered by the International Committee on Bacteriological Nomenclatures. The various comments, in general, fall into the following categories: 1) "Any attempt to classify taxonomically these pleuropneumonialike organisms is sure to be premature as we do not yet fully understand the cycle of development of any of them in artificial culture" (R. PSt. John-Brooks, J. C. G. Ledingham, and E. Klieneberger). 2) Taxonomic classification is advisable and needed but that the one suggested is contrary to the rules of priority in nomenclature and to the principle of naming the family from the type genus, and the order from the type family (R. E. Buchanan). 3) That the properties and characteristics of the class Schizomycetes need not necessarily exclude the micro6rganisms of the pleuropneumonia group (R. E. Buchanan). 4) That the attempt to classify micro6rganisms into genera according to the host of origin has not found favor in the past (R. S. Breed and R. St. John-Brooks). 5) That nomina hybrida have been used. Since the comments about the laws of priority and principles of nomenclature are the only ones in which it is possible to appeal!331

2 332 ALBERT B. SABIN to rules, it may be advisable to review the various attempts at nomenclature of the pleuropneumonia group. During the years that the micro6rganism of bovine pleuropneumonia remained a unique individual in the microbial world it received many names which varied with the author's concepts of its nature. Thus, while Bordet (1910) was the first to recognize its morphological complexity and considered its relationship to vibrios and spirochetes, Borrel et al. (1910), believing it to be essentially of coccal nature, devised the binomially correct Asterocoecus mycoides. As other investigators differed with the morphological concept of Borrel et al., new names were proposed as follows: Coccobacillus mycoides peripreumoniae (Martzinovski, 1911) Micromyces peripneumoniae bovis contagiosae (Frosch, 1923) Mycoplasma peripneumoniae (Nowak, 1929) Asteromyces peripneumoniae bovis (Wroblewski, 1931) It may be pointed out, however, that, quite aside from the question of priority, three of these names are invalid because they were proposed as polynomials, and only Mycoplasma peripneumoniae (Nowak) would require consideration in the event that Asterococcus mycoides proved to be invalid. In 1931, Wroblewski named the new member of the group, the infectious agent of contagious agalactia of sheep and goats, Anulomyces agalaxiae. In 1933, Ledingham referred to the confusion of names and suggested that the two microorganisms known at that time be placed in the order Actinomycetales and in the family of Actinomycetaceae. While he suggested that a new genus be set up to include the micro6rganisms of bovine pleuropneumonia and of agalactia of sheep and goats as species, he thought that the selection of an appropriate name should await further consideration and research. Turner (1935) disagreed with Ledingham and proposed the new order Borrelomycetales, family Borrelomycetaceae, genus Borrelomyces. In 1936, Shoetensack named the new micro6rganisms from dogs, Asterococcus canis. Since then many new related micro6rganisms have been isolated and the existence of a distinct microbial group became apparent. In 1939, however, the editors of the 5th edition of Bergey's Manual of Determinative

THE PLEUROPNEUMONIA GROUP 333 Bacteriology decided to leave out Asterococcus, among certain other previously recognized genera, because "the organisms included in these genera are little known and

3 THE PLEUROPNEUMONIA GROUP 333 Bacteriology decided to leave out Asterococcus, among certain other previously recognized genera, because "the organisms included in these genera are little known and they have not been generally recognized in later classifications." The classification and nomenclature of the pleuropneulmonia group which I suggested is the first one based on an analysis of the numerous species which have come to light in recent years, and I should deem it unfortunate indeed, if the laws of priority would "freeze" the many new names that I have suggested despite the fact that they may be out of place in a more reasonable classification that may be devised later on. The following considerations formed the basis of the suggested classification and nomenclature: 1) The microorganisms of the pleuropneumonia group can be regarded as sufficiently distinct from the bacteria to be dealt with in a separate class. 2) They are readily distinguished into parasitic and saprophytic groups. 3) The parasitic group can further be differentiated into genera which remarkably enough vary with the host that is parasitized. 4) A number of distinct species may exist in a single host, thus providing a varying number of species for each genus. The divisions were made and the names selected with these considerations mind, because they seemed to supply a more easily remembered and logical scheme than that in which the names of the family and order would have been derived from the name of the type genus. (The order Eubacteriales appears to have been established without derivation from below, i.e., from a type genus and family.) Similarly because the Latin roots of dog, rat, mouse, etc. are more familiar than the Greek, it seemed to me to be one instance where hybridization might be helpful and perhaps even desirable. While I consciously deviated from custom in suggesting this scheme, I must confess that I failed to realize the real legal claim of Asterococcus mycoides and the influence which that would have on any classification of the "pleuropneumonia" group. The main objection that I have to the name Asterococcus mycoides and to

4 334A ALBERT B. BABIN deriving the names of the family and order from it, is that in intimating a coccal nature for the group it not only gives a misleading concept of the essential characteristics of these microbes, but also tends to create confusion by suggesting a morphological relationship to other cocci which does not exist. However, according to Art. 15 of the Rules of Nomenclature, "the purpose of giving a name to a taxonomic group is not to indicate the characters or the history of the group, but to supply a means of referring to it," and according to Art. 59, "A name or epithet must not be rejected, changed, or modified merely because it is badly chosen, or disagreeable or because another is preferable or better known." Furthermore, it is doubtful whether even a broad interpretation of Art. 63 which says: "A name of a taxonomic group must be rejected when its application is uncertain" could be invoked in this case. Should it finally be decided that the name Asterococcus mycoides cannot be invalidated, my inclination would be to select Anulomyces (from Anulomyces agalaxiae, Wroblewski, 1931) as the type genus and to reconstruct the original classification in accord with the rules of priority and accepted principles of nomenclature as follows: Clams Paramycetes Order I. Anulomycetales Family I. Anulomycetaceae Genus 1. Anulomyces Type Sp. A. agalxiae Genus 2. Asterococcus Type Sp. A. mycoides Genus 3. Canomyces Type Sp. C. canis Genus 4. Murimyces Type Sp. M. pulmonsi Genus 5. Muscuomyces Type Sp. M. neurolyticus Family II. Sapromycetaceae Genus 1. Sapromyces Type Sp. S. laidlawi

THE PLEUROPNEUMONIA GROUP 335 ADDITIONAL REFERENCES FROSCE, P. 1923 Die Morphologie des Lungenseucheerregers. Arch. f. Wi8- sensch. u. Prakt. Tierheilk., 49, 35-48; 273-282.

5 THE PLEUROPNEUMONIA GROUP 335 ADDITIONAL REFERENCES FROSCE, P Die Morphologie des Lungenseucheerregers. Arch. f. Wi8- sensch. u. Prakt. Tierheilk., 49, 35-48; MAIRZNOVSKI, E.-J De 1'etiologie de la p6ripneumonie. Ann. Inst. Past., 25, SABIN, ALBERT B The filtrable micro6rganisms of the pleuropneumonia group. Bact. Rev., 5, 1-6.

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