<i>Staphylococcus aureus</i> Exotoxin Has Limited and Transient Effects on Cochlear Electrophysiology

Abstract

Seven ears of Sprague-Dawley rats were exposed to 20 µl Staphylococcus aureus exotoxin suspension by injection via the tympanic membrane into the round window niche. Another 6 ears were exposed to 20 µl broth as controls. ABR was performed in the interval 2–31.5 kHz immediately before and 1, 2, 5, 7 and 10 days after the exposure. Although threshold changes could be found in the toxin-exposed group but not the control group in the frequency range 10–20 kHz, there were only statistically significant threshold changes – at 31.5 kHz – on the 1st, 2nd, 5th, and 7th days after the exotoxin injection. S. aureus exotoxin has minor transient but reversible effects on the inner ear, causing chiefly high-frequency threshold and latency changes.

Dexamethasone Modifies the Effect ofPseudomonas aeruginosaExotoxin A on Hearing

“…In the present study the degree of hearing impairment and recovery time in group C rats was almost the same reported by Stenqvist. Healing of tympanic membrane was not observed in some rats in groups B and D, but a small perforation did not cause hearing impairment in a previous experiment performed in our laboratory (5).…”

“…Nevertheless, the cause of SNHL associated with AOM and CSOM is still not known, though some investigators claim that certain kinds of bacterial toxins cause SNHL in experimental animals, e.g. Haemophilus influenzae Type b Endotoxin (3), Escherichia coli lipopolysaccharide (4), Staphylococcus aureus Exotoxin (5) and Pseudomonas aeruginosa Exotoxin A (PaExoA) (6,7). Pseudomonas aeruginosa is one of the most common bacteria in cultures from patients with CSOM (8).…”