Patients with dangerous bacterial infections are at a higher risk for hearing loss than was previously thought, researchers at Oregon Health & Science University have found. Inflammation from the bacterial infections significantly increased susceptibility to hearing impairment via the raised uptake of aminoglycoside antibiotics into the inner ear, say the researchers.
Peter S. Steyger, Ph.D., professor of otolaryngology, head and neck surgery, of Oregon Health & Science University School of Medicine, said:
“Currently, it’s accepted that the price that some patients have to pay for surviving a life-threatening bacterial infection is the loss of their ability to hear. We must swiftly bring to clinics everywhere effective alternatives for treating life-threatening infections that do not sacrifice patients’ ability to hear. Most instances in which patients are treated with aminoglycosides involve infants with life-threatening infections. The costs of this incalculable loss are borne by patients and society. When infants lose their hearing, they begin a long and arduous process to learn to listen and speak. This can interfere with their educational trajectory and psychosocial development, all of which can have a dramatic impact on their future employability, income and quality of life."
Aminoglycosides, antimicrobials that are vital in treating life-threatening bacterial infections, are toxic to the ear. They are relied on by physicians to treat meningitis, bacteremia and respiratory infections in cystic fibrosis, but aminoglycosides kill the sensory cells in the inner ear which detect sound and motion.
At particular risk are infants in neonatal intensive care units (NICUs).
Each year, approximately 80 percent of 600,000 admissions into NICUs in the United States receive aminoglycosides. The rate of hearing loss in NICU graduates is 2 to 4 percent compared with 0.1 to 0.3 percent of full-term births from congenital causes of hearing loss.
In the sudy, healthy mice gievn a low amount of aminoglycoside experienced a small degree of hearing loss. When the mice had an inflammation that is typical of the infections treated with aminoglycosides in humans, the mice experienced a vastly greater degree of hearing loss.
The study paves the way to improving care guidelines for patients receiving aminoglycosides. To protect patients’ hearing, the researchers called for the development of more targeted aminoglycosides and urged clinicians to choose more targeted, non-ototoxic antibiotics or anti-infective drugs to treat patients stricken with severe infections.
Ja-Won Koo, Lourdes Quintanilla-Dieck, Meiyan Jiang, Jianping Liu1, Zachary D. Urdang, Jordan J. Allensworth, Campbell P. Cross, Hongzhe Li and Peter S. Steyger Endotoxemia-mediated inflammation potentiates aminoglycoside-induced ototoxicity Science Translational Medicine 29 Jul 2015: Vol. 7, Issue 298, pp. 298ra118 DOI: 10.1126/scitranslmed.aac5546
_Illustration: Cochlear coils, containing hair cells. Credit: Steyger lab, OHSU _