MRSA 'Superbug' Becoming More Resistant

Finding an antibiotic that works is not as easy as it used to be because bacteria grow more virulent over time. In a lab at the University of California at San Fransisco, where the latest and most aggressive MRSA strain, USA300, was discovered, researchers match patients with antibiotics they hope will cure them.

Using bacteria from infected patients, Dr. Jeff Brooks grows ''lawns'' of germs in petri dishes and adds tiny spots of antibiotics. He then waits 24 hours to see what works on that particular strain. The results show how complicated finding an antibiotic can be. After all, bugs such as MRSA are organisms whose very DNA is designed for survival.

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.

'Too Quick to Give Antibiotics?'

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.