ACUTE OTITIS-MEDIA INCREASES MIDDLE-EAR SUSCEPTIBILITY TO NASAL INJECTION OF PSEUDOMONAS-AERUGINOSA

Pseudomonas aeruginosa was injected intranasally into four groups of c hinchillas to determine if these bacteria can invade the middle ear by was of the eustachian tube. One group completed penicillin treatment of bilateral penumococcal otitis media (POM), and the second group sta rted penicillin treatment of bilateral POM at the time of P. aeruginos a injection. A third group had no POM, but completed a course of penic illin treatment before P. aeruginosa injection, and a fourth group had no POM and received no penicillin. Middle ear susceptibility to nasal ly injected P. aeruginosa was significantly higher in animals with POM (61%) than in animals without POM (32%, p = 0.001). Forced eustachian tube opening pressures did not correlate with P. aeruginosa susceptib ility. Thus, P. aeruginosa, the principle pathogen of chronic suppurat ive otitis media, can invade the middle ear by way of the eustachian t ube, and acute otitis media predisposes to middle ear infection by P. aeurginosa.