In the pursuit of managing antibiotic-induced hearing loss, researchers at Oregon Health & Science University observed that people suffering from severe bacterial infections are at a higher risk of hearing loss than previously assumed. As reported in the journal Science Translational Medicine, inflammation caused by these infections increases the susceptibility for hearing loss due to increased uptake of aminoglycoside antibiotics into the inner ear.

Aminoglycosides Can Be Harmful

Aminoglycosides – antimicrobials crucial for treating life-threatening bacterial infections – are lethal to the ear. Physicians generally use these drugs to cure meningitis and infections occurring in cystic fibrosis, failing to manage the consequent death of sensory cells inside the inner ear; those involved in the detection of sound and movement.

Infants in NICUs (infant intensive care units) are particularly at a higher risk. Annually in the US, about 80 percent of the 600,000 infants admitted in the NICUs are given aminoglycosides. This attributes to the 2 to 4 percent rate of hearing loss found in NCIUs, as opposed to the 0.1 to 0.3 percent that occurs in full-term babies born with congenital defects.

However, due to their cost-effectiveness and easy availability, aminoglycosides are still in frequent use around the world. The clinical use of aminoglycosides is somewhat limited, since the risks of acute kidney poisoning and permanent loss of hearing are well-documented. Yet, when it comes to potentially fatal bacterial infections, these antibiotics are life-saving options.

Confirming The Statistics

Peter S. Steyger, Ph.D., Professor of Otolaryngology, Head and Neck surgery, Oregon Hearing Research Center, Oregon Health & Science University School of Medicine, along with colleagues, gave healthy mice small doses of aminoglycosides. They observed that the mice experienced acute hearing loss. In cases where the mice had an inflammation, similar to that in human infections, administering aminoglycosides caused the mice to suffer from a greater degree of hearing impairment.

Prognosis

“The costs of this incalculable hearing loss are borne by patients and society. When infants lose their hearing, they begin a long and arduous process of developing the skill of listening and speaking. This can interfere with their educational and psychosocial development, all of which can have a dramatic impact on their future employability, income and quality of life”, commented Steyger.

The results of this experiment call for improving the standard guidelines for patients treated with aminoglycosides. To help protect hearing, researchers suggest the development of more target-specific aminoglycosides. They also urge clinicians to choose more specific and non-toxic antibiotics or anti-infective medicines to treat patients suffering from chronic bacterial infections.