Anyone who doubts the existence of evolution can see it in action in "superbugs," the bacteria that kill an estimated 90,000 people a year in this country, according to the Centers for Disease Control and Prevention.
These bacteria, formally known as methicillin-resistant Staphylococcus aureus, or MRSA, infect about 12-million Americans annually.
First identified in 1961 in the United Kingdom, these bacteria are the product of ordinary mutations that allow them to survive exposure to antibiotics. A new antibiotic might be able to kill them, but after a few generations, a few of the MRSA will develop resistance to that one too.
Eventually, these strains of bacteria will thrive no matter what is thrown at them, including methicillin, a highly effective derivative of penicillin.
"MRSA has been increasing for 10 to 15 years," said Dr. Todd Wills, an infectious disease specialist at the University of South Florida. "It has become something we need to recognize early on."
Two strains of drug-resistant staph bacteria have developed independently:
- The one found commonly in health care settings such as hospitals and nursing homes can get into the bloodstream and cause death.
- Another kind of the bacteria causes skin infections that generally begin with what looks like a small spider bite but which quickly becomes red, swollen and painful.
In the past, doctors could knock out an infection by prescribing almost any antibiotic. With drug-resistant bacteria proliferating, however, doctors often must know exactly what specific bacterium is causing the problem.
"With MRSA, we tend to shy away from using the big-gun antibiotics first," said Wills, who also is on the staff at Tampa General Hospital. "We don't want to push the bacteria into developing resistance" to these medications.
If that happens, the patient can be left harboring bacteria that cannot be killed with any known antibiotic - potentially a fatal predicament.
Though most of us harbor dangerous bacteria, especially in our nasal passages, our immune system has little trouble killing them.
"Maybe 60 percent of people carry staph bacteria and don't even know it," said Wills.
People who are sick, however, or who have a weakened immune system because of chemotherapy or an organ transplant, provide bacteria with an opportunity to multiply unchecked. Hospitals are an ideal breeding ground for these dangerous bacteria.
Fortunately, antibiotics are not the only weapon for treating infections.
"If you can mobilize the body's own defenses, that helps," said Wills. "We're moving away from the golden age of antibiotics - where we thought could take care of everything - to an age where antibiotics are just part of the strategy for fighting infection."
Freelance writer Tom Valeo writes about medical and health issues. Write to him in care of Pulse, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731, or e-mail email@example.com.