MONDAY, March 10, 2003 (HealthDayNews) -- By July 2004, nearly two-thirds of the common strains of the bacteria that cause infections ranging from middle ear problems to meningitis may be resistant to both penicillin and erythromycin in some parts of the United States.
At least that's what Harvard University researchers believe.
In a study published in the March 10 issue of Nature Medicine, the scientists used a mathematical model to predict how certain antibiotic-resistant strains of Streptococcus pneumoniae would develop.
Overall, they found that 41 percent of S. pneumoniae would be resistant to penicillin and erythromycin if no changes occur in the way antibiotics are used in the eight sites studied across the United States. Much of the problem is due to inappropriate use of antibiotics for sicknesses that don't respond to the drugs, such as the common cold and other viral infections.
S. pneumoniae are responsible for most ear infections, sinus infections, pneumonia, meningitis and blood infections. These bacteria are not, however, responsible for strep throat.
"The patterns of antibiotic use and misuse in this country have led to increasing resistance and these data suggest that the more use and misuse there is, the more resistance you'll have in your local area," says study author Marc Lipsitch, an assistant professor of epidemiology at the Harvard School of Public Health.
Lipsitch and his colleagues studied eight different types of S. pneumoniae. Within each type, there were hundreds to thousands of different strains of bacteria. The types the researchers chose to study are those most commonly resistant to antibiotics. And many of the bacteria are contained in the vaccine for S. pneumoniae.
The bacteria samples came from U.S. Centers for Disease Control and Prevention disease surveillance sites. States included in the samples were California, Connecticut, Georgia, Maryland, Minnesota, New York, Oregon and Tennessee.
One of the first things the researchers noticed was a wide variation in the amount of resistance between the sites. For example, in one sample 14.9 percent of the strains in New York were resistant to penicillin. In Minnesota, that number jumped to 30.9 percent. In Georgia, it was 53.7 percent, and in Tennessee nearly 80 percent of the strains were resistant to penicillin.
Lipsitch says the researchers found that differences in antibiotic use were likely to blame for the geographic variations.
Next, they tried to predict how rapidly these strains would mutate into antibiotic-resistant strains. Lipsitch says the researchers tried to take into account the trends that have occurred in resistance when they developed their predictions.
If no changes occur in the way people take antibiotics and more people don't take advantage of the effective, but expensive vaccine, about 41 percent of the strains studied at all of the sites will be resistant to penicillin and erythromycin by the summer of 2004. In Georgia, the researchers suspect that 65 percent of the strains included in the vaccine will be dually resistant. In Minnesota, that number will be around 67 percent. That means that resistance will have increased in those two states by 28 percent and 16.5 percent, respectively.
Does this mean we're doomed to a future of antibiotic-resistant superbugs? Maybe not, says Dr. Philip Tierno, head of microbiology and immunology at New York University Medical Center and author of The Secret Life of Germs. Tierno likens this study to the classic Charles Dickens' tale, A Christmas Carol.
"It's a vision of what the future could be," says Tierno, who says there's still time to change.
"Don't petition your doctor for unnecessary antibiotics," he suggests, adding that of the 90 million antibiotic prescriptions written each year, about 60 million aren't necessary.
However, Tierno says resistance will always be a problem because bacteria are constantly adapting. Humans have to be smarter, he says, which is why we need to continue developing new drugs and using vaccines whenever they're available.
More information
To learn more about antibiotic resistance, visit the U.S. Food and Drug Administration or the National Institute of Allergy and Infectious Diseases.
