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CDC's Gerberding Warns of Anti-Microbial-Resistant Infections
By Rich McManus
On the Front Page...
CDC director Dr. Julie Gerberding warned a crowded Lipsett Amphitheater audience Feb. 11 of a rise in antimicrobial-resistant infections, specifically of Staphylococcus aureus, in both hospitals and the community. "It's a very major problem in the health care setting...and is increasing in non-clinical settings as well," she said at a special session of Clinical Center Grand Rounds dedicated to Contemporary Clinical Medicine: Great Teachers.
While the discovery of two isolates of vancomycin-resistant staph in the past 2 years one in Pennsylvania and the other in Michigan "might not seem too urgent," Gerberding nonetheless cautioned that "biology is still marching forward." And while she also warned that "the pharmaceutical pipeline is shutting down" and no new magic-bullet antimicrobials are on the horizon, she was nevertheless encouraged by a "huge success story," namely that introduction of a pneumococcal vaccine for children has resulted in a large dip in the number of strains resistant to penicillin, which she called "unprecedented in the history of medicine."
Vaccination, not new antimicrobials, is the key to interrupting emergence of drug-resistant pathogens, she explained. If you can prevent infections in the first place, you don't have to worry about bugs outwitting drugs.
The fundamental problem with antimicrobials is that once pathogens develop resistance to them, the resistant strains come to predominate. Gerberding said CDC has come up with four steps to thwart the rise of drug-resistant pathogens. Prevention, of course, is key. "Far too little emphasis is placed on prevention of infection as the primary means of stopping antimicrobial resistance," she said.
Second, effective diagnosis and treatment are essential you have to know exactly what pathogen you are up against. Third, once you know what the enemy is, optimize antimicrobial use. Lastly, prevent further transmission of the agent causing the infection.
CDC has come up with a 12-step program to guide health care workers in minimizing the emergence of antimicrobial-resistant organisms. "We used the 12-step process because most clinicians are addicted to prescribing antibiotics," Gerberding quipped. "The first thing physicians need to do is recognize they have a problem!"
Gerberding didn't devote lecture time to the dozen steps; they are available on the CDC web site (and on handy cards that can be referenced by house staff) and are tailored to such populations as hospitalized adults, patients undergoing hemodialysis, and pediatric patients. But she did emphasize that vaccination is essential, where possible.
Staph infection is the most common cause of bacteremia in the United States, she reported. And a major culprit in transmitting this common flora is health care workers. She described the case of a physician with an upper respiratory infection who was unwittingly infecting, via aerosolized bacteria, patients throughout the hospital. "A simple surgical mask could have prevented the spread of infection," she said. When you have a cold, she continued, "you are lots more effective at transmitting whatever you have in your throat." She echoed the enduring advice of moms everywhere, including her own: "Stay home when you're sick. And cover your mouth when you cough."
Gerberding described some key milestones in medicine's battle to stay ahead of pathogens, beginning with the emergence of penicillin-resistant organisms in the 1960s, to organisms resistant to methicillin in the 1980s, to the rise of vancomycin-resistant bacterial species just last year. There is new evidence that resistance is also emerging to the powerful antimicrobial linezolid. "The bottom line to this story is, stay tuned," Gerberding said.
CDC epidemiologists learned much about community-acquired methicillin-resistant staph aureus (MRSA) when they examined outbreaks in both Pennsylvania and Mississippi. The Pennsylvania case occurred among 10 members of a college football team who suffered "turf burn" on the artificial grass where they practiced. It turned out that the college, for lack of funds, no longer laundered the athletes' towels, and that towel-sharing had become common.
In a Mississippi prison, use of soap for showers declined dramatically, leading to soap-less bathing. The CDC hence identified what Gerberding called "the five C's of community-acquired MRSA": contact, crowding, contaminated items, compromised skin integrity and cleanliness.
CDC's effort to discover the origins of the disease examined several hypotheses, reaching the conclusion that staph common in community settings had likely acquired the methicillin-resistance gene. The resistance gene, tracked with molecular biology, has several diabolical advantages, Gerberding related. "It's little, it's mobile, and it's deadly."
Her take-home message? Staph is still diversifying and evolving as time goes on. "Staph is not staph is not staph," she said, adapting Gertrude Stein to evolutionary biology. "They are not all alike. We should expect further adaptation to unique ecological niches."
She briefly mentioned a candidate vaccine for staph, but concluded that "new strategies are required, and not necessarily ones that cause the organism to die."
In response to questions after her lecture, Gerberding said: that no genetic predisposition to staph infection in humans appears to exist; that regular soap is in most cases just as good as antimicrobial soap since soap removes common transient bacteria; that alcohol-based hand gels are also effective and may get used more than handwashing does in health care settings; that antibiotic use in livestock is clearly a risk in promoting antimicrobial resistance; and that the emergence of microbes resistant to drugs is a looming problem in developing countries where antimicrobials can be purchased over the counter.
The entire talk may be viewed at www.videocast.nih.gov.
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