printable version5 Questions: Ellen Jo Baron on 'staph' outbreaks
Ellen Jo Baron
Tuberculosis, malaria and AIDS have become more challenging to treat with antibiotic drugs, but the problem of resistance extends beyond these killers. An example is staphylococcus aureus, often referred to simply as "staph," which is becoming resistant to all the drugs known to combat it. To get an overview of the current situation, Medical Center Report writer Mitzi Baker turned to pathology professor Ellen Jo Baron, PhD, the director of the clinical microbiology laboratories for Stanford Hospital & Clinics and Lucile Packard Children's Hospital.
1. MRSA—methicillin-resistant staphylococcus aureus—has been in the news recently. What is it?
Baron: Staphylococcus is a bacterium normally living on the skin and mucous membranes of mammals.
The kinds of diseases that it causes range from pimples and boils to systemic bacterial sepsis. It can colonize your heart valve, it can cause wound infections, it can cause osteomyelitis if it gets in the bones, and it can cause pneumonia. And it is painful: it has an enzyme that encourages the production of prostaglandins.
This is not a good bug to have. When penicillin came out in about 1945, staph was susceptible to it, but penicillin-resistant staph was seen as early as 1948.
Methicillin has a little bit more oomph than plain penicillin because of the side chains that make it more difficult for the bug to develop resistance, but it did not take that long—just about 12 years—for staph to develop methicillin resistance.
2. How much of a problem is this at Stanford?
Baron: Nationally, methicillin resistance among staph is at 60 percent. At Stanford, we are at about 29 percent of all the staph that we isolate from infections in the hospitals. But in the Emergency Department, the rate is 55 percent. These are community patients coming in, also those who have been in nursing homes.
3. If it has been a problem for a long time, why is it in the news now?
Baron: Since the methicillin resistance in the ED is so much higher than what we see in the hospital, we are recognizing first-hand community acquired MRSA as a problem, one that is being seen nationwide.
I just heard about a whole wrestling team in Michigan in which 22 percent of them have MRSA skin lesions, and we're seeing it more and more in jails.
I could speculate on why we are seeing more now. For one thing, there are more antibiotics in use, which produces antibiotic pressure that allows resistance to develop and continue. Also, one of the MRSA types in the community is more virulent, it causes more skin lesions and more pus, so it tends to spread more easily when there is contact. So in those populations like a wrestling team, or those in prison, there is no question that there is ample opportunity for it to spread.
4. How can we prevent MRSA? Why aren't there new antibiotics?
Baron: Wash hands frequently and avoid sharing personal items like razors, towels and clothes. Another thing that can be done is to limit the use of antibiotics.
But we also do need new antibiotics, ones that work in different ways to circumvent the ongoing resistance problem. Right now, there are 506 drugs in development, and only five are antibiotics. Why? Because the drug companies want to have a drug that you need to take for 10 years, 20 years, the rest of your life. They want a multimillion dollar drug—otherwise it isn't worth the $19 million it takes to develop a drug. If you take an antibiotic for 10 days, then you're done if it works. The shelf life of these drugs is not that long because the bugs develop resistance pretty quickly. It's really not worth it for a drug company to make an antibiotic. They don't get enough bang for their buck.
There is a lot of money for bioterrorism, which is so much less of a threat than this. There were a handful of anthrax cases. There are 1,000 people a day dying of multi-drug resistant tuberculosis, and there hasn't been a new drug for tuberculosis in 50 years. So it's just very depressing.
5. What about all the antibacterial products on the market that contain Triclosan? Are these helpful at all?
Baron: Soap and water works just as well to get rid of bad germs on your hands. There are no data showing that there are fewer infections or better outcomes with people using Triclosan-containing products than others, so there is no reason to add it to cleaning products. The widespread use of Triclosan is bound to increase bacterial resistance to staph and other organisms. It's a product that makes an effective advertising hook, feeding on people's fear of infections.