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Healthcare Infection Prevention
Community-acquired MRSA hampers empiric therapy
CDC cites common factors in outbreaks
At least three similar but distinct strains of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) are emerging in the United States, rendering common empiric therapy useless and causing aggressive skin infections, Healthcare Infection Prevention has learned.
As cases continue to appear in athletes, inmates, and men who have sex with men, the Centers for Disease Control and Prevention (CDC) is drawing increasing questions from a concerned public.
"If MRSA becomes a common cause of community skin infections, then it will really present a challenge to clinicians in choosing appropriate therapy," says Dan Jernigan, MD, medical epidemiologist in the CDC division of health care quality promotion.
The infections are fully susceptible to antibiotics such as tetracyclines and sulfa drugs, but the problem is that empiric therapy in the community typically does not include those drugs.
"The challenge is that clinicians have to chose antibiotics before they know what they are treating," he says. "If you are to treat this with the standard therapy — such as penicillins and cephalosporins — those antibiotics do not treat this kind of staph aureus."
Distinctly different strains
CA-MRSA strains are distinctly different from nosocomial varieties and appear to cause more severe skin infections.
"The antibiotic susceptibility patterns are milder [than nosocomial strains]," Jernigan continues. "But there may be some increased amount of skin abscess disease. It may have a propensity for more abscess-causing disease. It is still a little early to say, but there is a sense that not only does it have a unique [resistance] pattern, but also it may have some unique skin disease characteristics," he says.
CA-MRSA infections typically are limited to the skin and do not result in severe disease such as bloodstream infection.
However, CA-MRSA can cause severe illness even when treated quickly, as in the report of four children who died from community strains in 1999. In addition, people with compromised immune systems may be at risk for more severe illness if they get infected with CA-MRSA.
The CDC is working with state health departments to augment a national surveillance program for invasive CA-MRSA infections. The agency is using data collected in outbreak investigations in correctional facilities, in athletic teams, in children, and from sporadic cases to learn about strain characteristics, risk factors for disease, and prevention measures.
Five common C’ factors
Five factors — all beginning with the letter C for educational purposes — have been identified as common to the outbreaks of CA-MRSA, says Jernigan. Those factors are:
1. Compromised skin. "We know that in military recruits and football players and in some settings in prisons, people have skin problems, abrasions from scrapes, or they have existing skin disease," he says.
2. Contact. "With wrestlers and football players, there is frequent and very vigorous skin-to-skin contact," Jernigan says.
3. Contaminated surfaces and shared items. "These include sports equipment and weight-lifting equipment in prisons," he says.
4. Crowding. "We know that when people are very close to one another, it increases the likelihood of skin-to-skin contact and contamination of the environment," Jernigan explains.
5. Cleanliness. "We know that in prisons it is difficult to ensure that the best hygiene can be practiced," he points out. "With football players, too, there may be less-than-optimal showering conditions, use of soap, and cleaning of equipment.
"We know these five factors are common across the different groups that we have been investigating," Jernigan says.
"Interventions should be targeted to address these. There are things that can be done other than simply changing antibiotics," he adds.