INDUCTION OF TEMPORARY OTITIS-MEDIA IN SPECIFIC-PATHOGEN-FREE PIGS BYINTRATYMPANIC INOCULATION OF MYCOPLASMA-HYORHINIS

Objective-To examine whether Mycoplasma hyorhinis inoculated into the tympanic cavity can cause otitis media in pigs. Animals-17- or 22-day- old specific-pathogen-free pigs. Procedure-Histologic and bacteriologi c examinations were performed on specimens from the tympanic cavity an d auditory tube at 0, 7, 14, and 25 days after intratympanic inoculati on of M hyorhinis (auditory tube cloning strain 14). Results-In M hyor hinis-inoculated pigs, mild to moderate inflammation of the auditory t ube and tympanic cavity first appeared at postinoculation day (PID) 7. In pigs euthanatized at PID 14, the degree of inflammation was aggrav ated. Immunohistochemical analysis revealed M hyorhinis antigens on th e luminal surface of the auditory tube and tympanic cavity. By PID 25, lesions had lessened. By use of transmission and scanning electron mi croscopic examinations, mycoplasmal organisms were identified among th e cilia in the auditory tubes at PID 14 but not at PID 25. Results of bacteriologic examination indicated that 10(4) to 10(6) color-changing units of M hyorhinis were isolated from the tympanic cavity at PID 0. Variable numbers of M hyorhinis were isolated at PID 7 and 14, and nu mbers were decreased at PID 25. Conclusions-M hyorhinis inoculated int o the tympanic cavity can cause a self-limiting otitis media in SPF pi gs.