Alternative to antibiotic that damages hearing

A safer version of a potent antibiotic that often causes hearing loss has been developed by scientists.

An estimated 20% to 60% of all patients treated with aminoglycoside antibiotics — including newborns — experience irreversible partial or complete deafness.

Now researchers have produced a modified version of one of the drugs that works effectively in mice without causing hearing loss or kidney damage, another common side effect.

Aminoglycosides, which include streptomycin and gentamicin, are widely used to treat serious infections and sepsis, a deadly condition marked by the immune system going into overdrive. They are also given to infants with life-threatening infections.

But the drugs have serious side effects, including hearing loss due to the destruction of inner ear hair cells that help turn sound vibrations into nerve signals.

Anthony Ricci, from Stanford University in the US, said: “If we can eventually prevent people from going deaf from taking these antibiotics, in my mind, we will have been successful. Our goal is to replace the existing aminoglycosides with ones that aren’t toxic.”

Having successfully completed tests in mice, the team hopes to move onto patient trials “as soon as possible”.

The scientists took four years to produce five grammes of the newly patented antibiotic N1MS, derived from the aminoglycoside drug sisomicin.

Results published online in the Journal of Clinical Investigation showed that N1MS cured urinary tract infection in mice as effectively as sisomicin, without resulting in deafness.

The solution to the hearing loss problem lay in producing drug molecules that were unable to enter the hair cells through ion channels. These are cell membrane pores that allow the passage of electrically charged particles.

Co-author Alan Cheng, also from Stanford, said: “As a clinician-scientist, I treat kids with hearing loss. When a drug causes hearing loss it is devastating, and it’s especially disturbing when this happens to a young child as they rely on hearing to acquire speech.

“When I came to Stanford seven years ago from the University of Washington, I was exploring the angle that maybe we could add drugs to protect the ear from toxicity. Tony brought up this new idea: Why don’t we just not let the drug get in? Great idea, I thought.”

The scientists tested nine different compounds derived from sisomicin. All were significantly less toxic to hair cells than the original drug and three matched sisomicin’s ability to combat E. coli bacteria. N1MS turned out to be the most effective.

Aminoglycosides are a mainstay treatment for many infectious diseases, including pneumonia, peritonitis and sepsis. They are often used when other antibiotics fail to treat infections of unknown origin.