Effect of Pseudomonas aeruginosa exotoxin A on inner ear function.
Electrophysiological changes were studied in the albino rat following instillation of Pseudomonas aeruginosa exotoxin A into the middle ear cavity through the tympanic membrane. Hearing threshold was measured by a burst-elicited, frequency-specific auditory brainstem response (ABR) technique prior to exposure, then 24 and 48 h, 5 days, 2 and 4 weeks after the toxin instillation. A single dose (1 microgram/20 microliters) of Pseudomonas aeruginosa exotoxin A raised the ABR threshold over the whole frequency range, by 5-25 dB, particularly in the high tones. All threshold shifts were of combined conductive and cochlear type, reversible, with deterioration starting at 24-48 h and recovery at 2-4 weeks. Effusion of serous fluid occurred at 24 or 48 h, resulting in conductive hearing loss. Latency/intensity curves revealed a cochlear component in addition to conductive hearing loss. Morphological examination by SEM showed slight and inconsistent derangement of OHCs. It is concluded that Pseudomonas aeruginosa exotoxin A causes middle ear inflammation, facilitating penetration to the inner ear and that this toxin also reversibly affects cochlear function.
Stenqvist
M
M
Department of Oto-Rhino-Laryngology and Head and Neck Surgery, University Hospital, Uppsala, Sweden.
Anniko
M
M
Pettersson
A
A
D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins; D003051:Cochlea / Q000503:physiopathology; D007758:Ear, Inner / Q000503:physiopathology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005098:Exotoxins / Q000096:biosynthesis / Q000633:toxicity*; D006314:Hearing Loss, Conductive / Q000209:etiology* / Q000503:physiopathology; D006319:Hearing Loss, Sensorineural / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D010035:Otitis Media, Suppurative / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A