Genetic mutations and aminoglycoside-induced ototoxicity in neonates

Objective: Mutations in the 12S rRNA gene have been associated with aminoglycoside-induced ototoxicity. Our objective was to study the relationship of these mutations in neonates, duration of aminoglycoside exposure, and other known risk factors to the presence of hearing loss.

Study design: Prospective case-cohort study.

Setting: Three neonatal intensive care units (NICUs) in Cincinnati, OH.

Subjects and methods: We studied a population of premature, low-birth-weight (< 2500 g) infants admitted to one of three ICUs. Demographic, genetic, clinical, and audiometric data were collected, and the prevalence of 12S rRNA mutations was calculated.

Results: Of the 436 patients enrolled in the study, 378 were exposed to gentamicin during their ICU stay. Mutations in the 12S rRNA gene were identified in four patients (0.9%), all of whom received gentamicin. Of the cohort, 256 patients (60%) received a complete audiometric assessment; 39 failed their initial hearing assessment. Only one of these patients had a 12S rRNA mutation. Of these 39 patients, the mean birth weight (1645 g vs 1306 g) was significantly less than the birth weight of those infants who passed their initial hearing screening. Definitive hearing assessment for those who failed showed no significant differences, however.

Conclusion: The prevalence of 12S rRNA mutations related to aminoglycoside ototoxicity in our study population was approximately one percent. Most patients with this mutation and aminoglycoside exposure showed no evidence of hearing loss. Low birth weight was one risk factor related to the presence of failing a hearing assessment.