Ed Ungar, Medical Tribune News Service
Researchers in Toronto have established that bacterial infection
causes heart disease in rabbits. They suggest a similar mechanism
is at work in humans.
They found that rabbits infected with Chlamydia pneumoniae
bacteria developed atherosclerosis in the main artery of the heart
more than one-third of the time. Those rabbits that received early
treatment with the antibiotic clarithromycin developed heart
disease only 8.3 percent of the time.
Rabbits whose antibiotic treatment was delayed developed
atherosclerosis at a 12.5 percent rate. The study was presented
September 27 at the Interscience Conference on Antimicrobial Agents
and Chemotherapy in San Francisco.
Chlamydia pneumoniae is a common bacterium that has infected
most adults more than once. It can lead to pneumonia and is the
third most common cause of the disease. But in most cases people
are unaware when they've been infected by the bacterium.
``The infection isn't severe and it may be passed off as a
cold,'' said lead researcher Dr. Ignatius Fong, professor of
medicine at the University of Toronto and chief of infectious
diseases at St. Michael's Hospital in Toronto. ``You may have
sniffles and a cough. But it's difficult to tell if it's from a
virus or a bacterium.''
The infected rabbits in the study did not get very ill. ``That
may mimic what happens in humans,'' said Fong. ``There's a good
chance based on these studies,'' he said, ``that if you started
antibiotic treatment early on, it would be more effective in
preventing damage to the blood vessel.''
``There is growing evidence to support the hypothesis that
Chlamydia pneumoniae has a role in either accelerating or causing
coronary heart disease,'' noted Dr. Donald Low, chief of
microbiology at Mt. Sinai Hospital in Toronto.
Low observed that there is also evidence that bacteria may
affect blood vessels that lead to the brain and thus cause stroke.
As for those who have already been infected, Fong said the
research in rabbits showed that even delayed treatment was
effective. ``It may be that we will have to treat people much
longer and at much higher doses,'' he said.
Fong cautioned that further research on both rabbits and humans
needs to be carried out. He said there is danger in antibiotics
being overprescribed, which allows resistant strains of bacteria to
evolve. Antibiotics also have side effects, including nausea and
upset stomach. Some women also develop yeast infections.
Human trials with patients who have heart disease are underway.
Fong suggested that one day a vaccine could be developed that
would protect young people from bacteria that can cause heart
disease in their old age. He added that a vaccine for those already
infected is also a possibility.
``If indeed the bacterium is an infectious agent,'' said Low,
then we should see if we can treat or even prevent bacteria-caused
heart disease. ``That's the million dollar question.''
