 A
widely-used treatment for chlamydial eye infection actually
makes people more susceptible to new infections, according
to a startling new study in the September 27 issue of
JAMA.
Trachoma, an eye disease brought
on by Chlamydia trachomatis, is the leading cause
of blindness in the developing world. Nearly a decade
ago, the WHO established the Surgery, Antibiotics, Facial
cleanliness and Environmental improvement (SAFE) program
to eradicate trachoma by 2020. Earlier studies showed
the antibiotic azithromycin to significantly reduce
inflammation with just one annual dose, and so it was
chosen for the antibiotic arm of the program. But this
new JAMA study is the first to look at its longterm
effects. "This is not what we expected," admits co-author
Dr Deborah Dean of the Children's Hospital & Research
Center Oakland in California.
BETTER
OR WORSE?
Trachoma is most common in children under the age of
10. It causes inflammation of the conjunctiva; if left
untreated the eyelashes can turn inward and stick to
the eye. If this isn't fixed with surgery, eventually
the patient can go completely blind.
Dr Dean and her team measured rates
of infection with Chlamydia trachomatis in three
rural communes in Vietnam, where as many as 17% of kids
are afflicted. Azithromycin was given to all infected
children in two of the communes; those in the third
got a different, topical ointment. While the antibiotic
was effective at clearing infection, the team found
that in the villages treated with azithromycin the number
of new cases actually increased over three years and
re-infections shot up fourfold compared to the ointment-treated
group. "The antibiotic seems to wipe out the infection
before the body has time to mount a protective immune
response," explains Dr Dean. "Those people are almost
immediately susceptible to reinfection."
CANUCK
CONNECTION
The findings were certainly disheartening, but not unheard
of. In fact Dr Robert Brunham, of the BC Centre for
Disease Control, published similar findings on sexually-transmitted
Chlamydia last year in the Journal of Infectious
Diseases. "We launched an azithromycin program in
BC in the mid 90s. Initially, the prevalence declined
by about 50%, but there are more infections now than
before the program was launched," he says. So should
we do away with azithromycin altogether? No, insist
Dr Brunham and Dr Dean. "No disease has ever been eradicated
by antibiotics alone," says Dr Dean. "This will renew
energy for the search for a vaccine."
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