A novel biodegradable pellet which slowly
releases antibiotics into the middle ear could transform the lives of thousands
of children who suffer from glue ear infection.
Scientists at The University of Nottingham
have developed the tiny 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% 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. Birchall
says: “Glue ear is one of the most common 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. We are
particularly concerned about children that have glue ear that comes back
despite grommet surgery—with risks of permanent damage to the ear drum or the
middle ear. This exciting new research to try to reduce the need for repeated grommet
insertion involves ENT surgeons, microbiologists, and pharmacists. Having such
a multidisciplinary team on board means that we can take advantage of all the
expertise available to help these children.”
Up to 80% of children are affected
temporarily by glue ear. Glue ear causes hearing impairment and subsequently
can affect speech and schooling. Glue ear can also be associated with frequent
ear infections. As many as 33,000 grommets are fitted in England and Wales every year. In Nottingham alone 300 to 400 children are referred to a
specialist—100 of them will require grommets. Whilst treatment with grommets is
effective, the grommets are designed to extrude after about nine months or so.
Unfortunately glue ear can return and one in five children will have to have
surgery again.
Glue ear happens when a thick mucus
collects inside the ear, at the other side of the ear drum. This interferes
with hearing and therefore with schooling, social development, and
relationships with friends and siblings. Following research by this group and
others, it is now recognized that glue ear is caused by biofilms—bacteria which
grow together in a protective ‘slime’. They are 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.
First, the team produced a biodegradable
pellet capable of doing the job. Mat Daniel,
MD, says: “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, they found a way of demolishing the
biofilm to make the infection easier to treat. This work has been the
responsibility of Saif Al-Zahid,
MD. He says: “Bacteria in
biofilms are held together in a strong matrix. 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.”
