Biodegradable pellet offers potential solution to glue ear

Scientists at Nottingham University have developed the controlled-release antibiotic pellet, which can be implanted in the middle ear during surgery to fit grommets, or small ventilation tubes.

Over a period of three weeks it will release effective quantities of antibiotics to target any infection which can, in up to 20 per cent of cases, result in children having to return for a second and sometimes a third operation.

The team has been led by John Birchall, professor of otorhinolaryngology, and Roger Bayston, associate professor of surgical infection, in the Faculty of Medicine and Health Sciences.

Prof Birchall said: ‘Glue ear is one of the commonest complaints that we see in children in the ENT clinic. The condition causes hearing loss, problems with speech or schooling, and often it is accompanied by repeated ear infections.’

According to Nottingham University, glue ear occurs when a thick mucus collects inside the ear — at the other side of the ear drum — and interferes with hearing.

Following research by this group and others, it is now recognised that glue ear is caused by biofilms — bacteria that grow together in a protective ‘slime’.

They are reportedly very difficult to treat because they are capable of turning off target sites for common antibiotics, becoming up to 1,000 times less susceptible. In a significant proportion of cases, antibiotics have only a temporary effect and repeated grommet operations are needed.

To counter this, the team produced a biodegradable pellet capable of doing the job.

Dr Mat Daniel said: ‘We tested antibiotics against biofilms in the laboratory but it rapidly became apparent that very much higher levels of antibiotics would be needed. Because of that we knew that giving antibiotics by mouth was not going to work. We developed this biodegradable antibiotic pellet so we could put it directly into the ear — where the actual infection is. We hope that in the future this may very much reduce the need for any children to have more than one operation.’

Next, team member Dr Saif Al-Zahid found a way of destroying the biofilm to make the infection easier to treat.

‘Bacteria in biofilms are held together in a strong matrix,’ said Al-Zahid. ‘We have recently found that the expectorant N-Acetylcysteine is able to break down this biofilm matrix effectively — thereby releasing bacteria to a free-floating planktonic form.

‘In doing so, antibiotics become much more effective in killing bacteria as the protective properties of a biofilm are no longer present. N-Acetylcysteine has an added benefit due to its mucus-reducing properties — this is desirable in glue ear as the middle ear is filled with a thick mucus secretion.

‘As a result, the addition of N-Acetylcysteine in our antibiotic pellet would be likely to increase the chance of eradicating middle-ear biofilms and speed up the resolution of glue ear.’