SHORT ARTICLES ELECTRONMICROSCOPICAL OBSERVATIONS ON MYCOPLASMAS

SEVER A L types of bovine pneumonia can be recognised pathologically, including cuffing pneumonia (Jarrett, 1956) and a significant association between Mycoplasma dispar and Ureaplasma spp. and cuffing pneumonia was demonstrated in a group of calves (Pirie and Allan, 1975). Both species have been shown to produce pneumonia experimentally (Gourlay and Thomas, 1969 and 1970; Gourlay et al., 1976; Howard et al., 1976), but microbiological and pathological studies on several groups of naturally infected calves suggested that M. dispar was the more important organism in cuffing pneumonia (Allan, Pirie and Selman, 1976). Preliminary findings of an electronmicroscopical study of bronchial and lung tissue of calves were reported by Allan et al. (1976) and statistical examination of the data suggested that the presence of M. dispar in bronchial tissue, confirmed by laboratory culture, increased the probability of detecting mycoplasmas in pneumonic lungs by electronmicroscopy. This paper extends the earlier work on the ultrastructure of mycoplasmas in pulmonary tissue from calves with pneumonia and describes the changes in the bronchial epithelium in animals with cuffing pneumonia. In addition, the finding of mycoplasmas with an extracellular capsule, an ultrastructural feature associated with M. dispar (Howard and Gourlay, 1974), will b