Bacterial and mycotic otological infections in Singapore

Hearing preservation with labyrinthine ablation in otitis media

OBJECTIVES

Iatrogenic fenestration of the inner ear in the presence of otitis media is commonly associated with permanent hearing loss. Hearing can generally be preserved when the vestibular labyrinth is ablated in a controlled manner in noninflamed ears. The purpose of this study was to examine the feasibility of hearing preservation with violation of the inner ear in the presence of middle ear inflammation.

STUDY DESIGN

Prospective and controlled animal model.

METHODS

Otitis media was induced bilaterally in pigmented guinea pigs with transtympanic injection of Streptococcus pneumoniae, nontypeable Haemophilus influenzae, or formalin-killed nontypeable H influenzae. Two to 4 days after injection, the horizontal canal of one ear was transected and sealed. Hearing was tested before and after labyrinthine ablation.

RESULTS

Otitis media was induced in all ears. Bacterial cultures were positive in 19 of 20 S pneumoniae-injected ears, and in 10 of 16 nontypeable H influenzae-injected ears. One week after surgery, elevation of click thresholds (> 15 dB) was encountered in none of the fenestrated or unfenestrated S pneumoniae-infected ears, in two of six unfenestrated and three of six fenestrated nontypeable H influenzae-infected ears, and in one of five killed-nontypeable H influenzae-injected ears both with and without fenestration.

CONCLUSIONS

These data suggest that ablation of a semicircular canal in the presence of middle ear inflammation or infection does not necessarily lead to profound sensorineural hearing loss. Hearing loss associated with iatrogenic violation of the semicircular canals may be more dependent on factors other than the presence of nonspecific middle ear inflammation.

Isolation of Cryptococcus neoformans var. neoformans from canine otitis

Cryptococcus neoformans was demonstrated in the clinical material of a 15-year-old male dog with a history of chronic otitis externa by employing Helianthus annuus seed agar as a selective medium. The examination of the isolate for sexual compatibility on modified Helianthus annuus seed medium revealed that it belonged to Filobasidiella neoformans var. neoformans 'alpha' mating type. In the authors' view, this appears to be the first report of isolation of Cr. neoformans var. neoformans from diseased ear of a dog.