Morphology and Nature of the Pleuropneumonia Group of Organisms

Abstract

Organisms of pleuropneumonia-like strains isolated from rats, mice and man often appear in young colonies as small bacilli with bipolar staining. The bacillary forms round up and may swell to large size. The large round forms either develop vacuoles and degenerate into empty blebs or reproduce small bacillary forms inside their membranes. The reproductive function of the round forms in the organisms of bovine pleuropneumonia has been observed by several authors. Occasional strains in many spp. of commonly occurring bacteria show a similar transformation into large round forms and a similar reproductive process by the development of bacteria in the large round forms. These processes belong to the general properties of bacteria and do not separate the pleuropneumonia group from bacteria. The bacterial strains which show the reproductive process characteristic of the pleuropneumonia group often show a similarity to these organisms in other respects such as softness, fragility and poor staining in dry prepns. The pleuropneumonia group presents no properties which are not shared by the bacteria; it belongs near the genera Pasteurella and Hemophilus.