A stable L-form of Haemophilus pleuropneumoniae.

A stable L-form of Haemophilus pleuropneumoniae (Shope) was isolated from primary pig kidney cell tissue cultures which had been inoculated 28 days previously with glycine induced spheroplasts of this organism.H. pleuropneumoniae was definitely cytopathic in primary pig kidney cell cultures, producing cell rounding, cytoplasmic vacuolation and nuclear enlargement with peripheral condensation of nuclear DNA. By contrast, the effect of spheroplasts was much less distinct, producing only loss of cytoplasmic granularity coincident with apparent loss of some cytoplasmic RNA, and slight nuclear enlargement. Both the organism and its L-form were shown to be related by cultural methods, antibiotic sensitivity tests, immunofluorescence and immunodiffusion. The L-form remained stable after 90 serial passages on agar and 45 in broth, each medium being capable of supporting the growth of both forms of the organism.