Deadly Germs Now
Resistant To 'Superbug' Drugs
New Strains Of Bacteria Multiplying Across Canada
By Brad Evenson
National Post
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.