-
- The germ that causes pneumonia, bacterial meningitis
and inner ear infections has grown resistant to the synthetic drugs that
doctors once hoped would contain the spread of so-called "superbugs,"
Canadian research has shown. As a result, new strains of bacteria have
multiplied across Canada than can no longer be destroyed by fluoroquinolones,
drugs developed in the mid 1980's to combat resistance to such medications
as penicillin and tetracycline.
-
- Researchers have found that 3.7% of Streptococcus pneumoniae
strains taken from Canadian patients have grown resistant to fluoroquinolones.
The leading cause of Strep. pneumoniae is often called the "Captain
of the Ship of Death" because its arrival is frequently a fatal complication.
The airborne bacteria is usually inhaled directly into the lungs but can
also be spread through physical contact.
-
- Until 1994, Strep. pneumoniae could be killed by fluoroquinolones.
Fluroquinolones work by blocking the DNA replication of bacteria, which
prevents them from multiplying in the body. But with breathtaking speed,
the new strains of Strep. pneumoniae have found some kind of survival
mechanism.
-
- "With this resistance, it also learns how to become
resistant to other fluoroquinolones," says Dr. Don Low, microbiologist-in-chief
at Toronto's Mount Sinai Hospital.
-
- "In fact, we have strains of Strep. pneumo that
are already resistant to drugs that have not yet come on the [commercial]
market."
-
- In an article in today's New England Journal of Medicine,
Dr. Low says over 7,500 samples of Strep. pneumoniae take between 1988
and 1998 show elderly people in Ontario are the leading carriers of the
new strains. Dr. Low blames the widespread use of fluoroquinolones to
treat seniors with bronchitis for the precipitous rise in the resistance.
What is more worrisome is that fluoroquinolones have recently been approved
for tests in the U.S. in treating children with middle ear infections,
also known as otitis media.
-
- Drug resistance has been a problem ever since British
bacteriologist Alexander Fleming discovered penicillin in the 1940s.
"Most antibiotics are made by bacteria," explains Dr. Low.
"And they kill other bacteria so they won't invade their space.
So most of them have been around for millions and millions and millions
of years, and bacteria have had an opportunity to become naturally resistant
to them."
-
- Fluoroquinolones were different; bacteria had never
seen them and scientists predicted germs would not easily be able to grow
resistant. The new drugs worked so well, their use skyrocketed from 48,000
prescriptions in 1999 to more than 330,000 last year. Dr. Low says this
pressure has forced Strep. pneumoniae to adapt at an alarming rate.
-
- "What is even more disconcerting is these things
are popping up everywhere, and it's not as if one particular strain as
spread through a community,' he says. "I think this is just a reflection
of usage."
-
- While only a small percentage of bacteria are now resistant,
the trait can spread very quickly. In 1989, only 2% of Strep. pneumoniae
samples in Canada were resistant to penicillin. Today, the rate is greater
than 40%. Dr. Low says similar rates of fluoroquinolone use in the U.S.
and Europe mean similar patterns are probably already emerging there.
However, he says the situation is not hopeless. Instead of using mild
antibiotics first when treating infections, doctors should consider using
the newest, most potent drugs in their arsenal as a first assault.
|
