Said Chambers: "They can mutate. They can adapt to virtually any pressure that we expose them to and the most important one now is antibiotics. From the bacteria point of view, antibiotics are the biggest problem they've had to face in their evolution and they're doing a good job of adapting."
There are antibiotics in the pipeline for some infections, including MRSA, but they are slow to arrive on the market and few are in a convenient pill form.
"The problem is oral drugs," Chambers said. "Most of these are not oral; they require intravenous administration."
That presents patients with a difficult and costly outlook for hospital treatment. The antibiotics that McQueary is getting right now are daptomycin and cephazolin.
"If I become resistant to the daptomycin, we don't know what we're going to do," she said.
Part of the problem is that developing antibiotics isn't a priority for pharmaceutical companies, according to the chairman of the University of California at San Franciso's Department of Clinical Pharmacy, Dr. Joseph Guglielmo.
"I would say for pharmaceutical companies, frankly, there is not as great a fiscal incentive to produce new anti-infectives as opposed to drugs for chronic disease states," he said. "And the reason for that is you give an antibiotic that may only be given for seven days. As opposed to, let's say a cholesterol-lowering drug, or an anti-depressant, which is given to you for the rest of your life, the fiscal return on the investment is better with those."
In fact, antibiotic development has dropped off dramatically. During the five-year period ending in 1987, the Food and Drug Administration licensed 16 new antibiotics. But in the five-year period ending in 2007, only five were approved.
The overuse and misuse of antibiotics is believed to be part of why the MRSA bug is growing so strong. There seems to be a general widespread practice of prescribing antibiotics for bacterial infections sometimes even before we are certain that the infection being treated is bacterial.
"We're too quick to give antibiotics," Chambers said, adding that the more we use them, the faster bacteria evolve to resist them.
"We would not have drug resistance if we did not have drugs. It's that simple," Chambers said. "Of course, we have to have antibiotics and antimicrobial drugs that are used to treat infections, but there is this tradeoff in using antibiotics."
Doctors regularly talk about a "post-antibiotic era" and if history is any indication, we are well on our way. The overprescribing and misuse of antibiotics have long been eroding their effectiveness.
Penicillin was the wonder drug of the 1940s, but now it is rarely prescribed. Cipro was once considered a miracle drug. In 1999, it worked on 95 percent of e-coli specimens. By 2006, it was effective only 60 percent of the time.
"When nature confronts an adversity there is a mutation that takes place to allow it to survive, and I think these bacteria are very simply trying to survive," Guglielmo said.
While doctors advise people to use antibiotics only when they're needed, the best prevention against MRSA is to wash hands with soap and water for at least 30 seconds at a time. It's a message that Peg McQueary has taken to heart