Personalised medicine: Genetic test shows mutation that leads to antibiotic-induced deafness

A genetic test gives results in half an hour to show if a person may become deaf in response to certain antibiotics, so can be used for babies with suspected sepsis who need treatment fast

By Clare Wilson

Occasionally, children go deaf as a result of antibiotic treatment. Now a rapid genetic test has been launched to identify those who are vulnerable to such ear damage, so that alternative antibiotics can be given.

The test delivers a result in 26 minutes, meaning it can be done quickly enough to guide what to do for babies with suspected sepsis, who need treatment as fast as possible.

About one in 500 people have a genetic mutation that means that the antibiotic gentamicin kills cells inside their ear. This is thought to cause about 14,000 people worldwide to go permanently deaf each year.

Despite the rare effect, gentamicin is the recommended treatment for sepsis – a life-threatening overreaction of the immune system to infection – because it is effective against the bacteria most likely to be the cause.

People known to have the mutation can be treated with different antibiotics called cephalosporins, which kill a broader range of bacteria. Because of this, cephalosporins are more prone to triggering antibiotic resistance, so aren’t as commonly prescribed.

To check for the genetic mutation, most hospitals currently use PCR-based tests, which can take days to return results. Guidance for treating babies with suspected sepsis in hospitals in England says antibiotics should be started within 1 hour of doctors recognising that treatment is needed.

The new assay, which Manchester University NHS Foundation Trust hospitals will start using routinely from next week, is faster because it uses a different genetic testing technique, called RT-LAMP.

Made by UK firm Genedrive, the test was used in two UK hospitals. Of 526 babies who needed treatment for suspected sepsis, the test failed to produce a result in 17 per cent of cases, but it identified three babies with the mutation that put them at risk of deafness, who all received the alternative antibiotic, according to a recently published trial. “We have got three people that will go through life with their hearing intact that would have been deaf if they had not had this [test], says David Budd at Genedrive.

Genetic tests such as this one should be more widely used, according to a report out this week from the British Pharmacological Society and the Royal College of Physicians. It found that there are 40 commonly used medicines where genetic tests could help guide treatment.

In future, babies could have a panel of such tests carried out when they are born, so there would be no waiting for results, says co-author Emma Magavern at Queen Mary University of London. “It would affect [their treatment] for the rest of their life.”

Journal reference: JAMA Pediatrics, DOI: 10.1001/jamapediatrics.2022.0187

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