FIELD ISOLATES OF MYCOPLASMA-OVIPNEUMONIAE EXHIBIT DISTINCT CYTOPATHIC EFFECTS IN-OVINE TRACHEAL ORGAN-CULTURES

Ovine tracheal ring explants were infected with lour different Mycopla sma ovipneumoniae and one ill. arginini field isolate and their abilit y to induce cytopathic effects was tested by measuring ciliary activit y and intracellular calmodulin release. Infected tracheal rings showed significantly decreased ciliary activity as compared to the non-infec ted control rings. There were, however, marked differences between iso lates in the onset and severity of the effects which correlated with t heir ability to produce hydrogen peroxide. Infected tracheal rings rel eased more calmodulin chan the non-infected controls. The amount of ca lmodulin released also varied between isolates, and somewhat reflected the degree of loss of ciliary activity in the corresponding rings ind uced ba the different isolates. Light and electron microscopic examina tions of infected tracheal rings revealed disorganisation and sloughin g of the epithelium, and association of mycoplasmas only with the cili a. Following repeated in vitro passages, the organisms had reduced abi lity to inhibit ciliary activity which correlated with decreased hydro gen peroxide production. Addition of catalase to the organ cultures de layed loss of ciliary activity. These results suggest that M. ovipneum oniae induced ciliostasis in ovine tracheal ring explants which correl ated with hydrogen peroxide production. Furthermore, these M. ovipneum oniae-induced injuries to respiratory epithelial cells could contribut e to the role that this organism map play in sheep respiratory disease .