CA-MRSA shown to be an emerging problem
Not as deadly as 'cousin,' but still merits vigilance
In the wake of a series of media warnings about the deadly health care-associated methicillin-resistant Staphylococcus aureus(MRSA) comes a new study in Annals of Emergency Medicine that outlines the emergence of its "cousin," community-associated MRSA (CA-MRSA).1 While the researchers note that CA-MRSA is very rarely fatal, they nonetheless declare that it merits the attention of ED managers.
The researchers, using merged National Hospital Ambulatory Medical Care Survey data from 1993-2005, identified ED visits with diagnoses of numerous skin infections. An abscess, for example, can be indicative of CA-MRSA. They found the following:
- "Infections of interest" were diagnosed in 3.4 million visits in 2005, vs. 1.2 million visits in 1993.
- As a proportion of all ED visits, such infections were diagnosed in 2.98% of ED patients in 2005, vs. 1.35% in 1993.
- When antibiotics were prescribed, those typically active against CA-MRSA were used increasingly during the study period, being used rarely in 1993 but rising to 28% in 2005.
How serious a threat is CA-MRSA? "You've got to remember we're talking about two different things: One is nosocomial, or hospital-acquired, the other is community-acquired [CA]," says Daniel J. Pallin, MD, MPH, lead author of the study. Pallin is director of clinical research at Brigham and Women's Hospital (BWH) in Boston, an attending ED physician at BWH and Children's Hospital, also in Boston, and an assistant professor of medicine and pediatrics at Harvard Medical School in Cambridge, MA.
When a patient is hospitalized and exposed to nosocomial MRSA, "this is often associated with serious bloodborne infections and is quite dangerous," he says. "It is also well documented to be spread in hospitals, particularly by clinicians' hands."
CA-MRSA, by contrast, often is contracted outside the hospital, and the vast majority of cases are skin infections, typically abscesses. "While these community-associated infections are certainly painful and unsightly, they are very rarely fatal or life-threatening," says Pallin. Still, he observes, "The rate of these infections among ED patients has gone up considerably, and we are probably seeing an epidemic."
David A. Talan, MD, chairman of the Department of Emergency Medicine, Olive View-UCLA Medical Center, Sylmar, CA, and professor of medicine at the David Geffen School of Medicine at the University of California Los Angeles, wrote an editorial on Pallin's study in the same issue of Annals. "Community- associated MRSA is not a deadly superbug," he wrote. He added, however, that the study's findings were ". . . compelling, and suggest that community-associated MRSA has resulted in a significantly increased burden of disease and that additional attention and resources should be directed to monitor, prevent, and control this emerging problem."
In light of the significant increase in CA-MRSA, "when patients come in with skin infections, you have to be aware of the possibility the bacteria causing those infections are resistant to the usual antibiotics," says Pallin.
There are two broad categories of infection: purulent and nonpurulent. The former, characterized by an abscess, is most likely these days to be caused by CA-MRSA, he notes. "The treatment is surgery," Pallin says.
However, when the abscess is surrounded by redness and hard, painful skin, then an antibiotic that is effective against MRSA also may be needed. "There are several, but probably the best is Bactrim [trimethoprim/sulfamethoxazole]," he says.
Other skin conditions such as folliculitis are sometimes not treated by surgery, but should be treated with agents effective against MRSA, Pallin continues. "For nonpurulent [non-puss] conditions, we don't know what antibiotics should be used," says Pallin. "Some physicians have started to use Bactrim, but others give cephalexin for conditions like cellulitis."
ED managers also should be aware that "it is not completely clear these bacteria [hospital-acquired and CA-MRSA] will continue to live in different environments," Pallin warns.
If the separation of these two disappears completely, he says, "We will see people who have not been in the hospital have a MRSA infection and not necessarily respond to what we expect them to," Pallin says. For example, hospital-acquired MRSA often is not sensitive to trimethoprim/sulfamethoxazole.
The two are not always easily distinguishable, says Pallin. "If you have a dialysis patient, you assume it's hospital-acquired, and if it's a high school wrestler with an abscess, you assume it's CA-MRSA, but the only way to tell for sure is to wait for culture results," he says.
There is a difference of opinion concerning when to do a culture, Pallin says. "When you talk about abscesses, some say there's already enough information out there to think they are probably caused by MRSA; that these patients don't need antibiotics anyway, so why bother to culture; or if they do need antibiotics, you give them Bactrim. So again, why bother to culture?" he says. "Others, including me, feel we are in a time of historical change, and my feeling is that all abscesses should be cultured."
These cultures are very inexpensive and very specific, Pallin notes. "If the patient does not get better after an operation, we can look at the labs and then know exactly what bacterium caused the problem and choose antibiotics appropriately," he explains.
Reference
- Pallin DJ, Egan DJ, Pelletier AJ, et al. Increased U.S. emergency department visits for skin and soft-tissue infections, and changes in antibiotic choices, during the emergence of community-associated methicillin-resistant Staphylococcus aureus. Ann Emerg Med 2008; 51:291-298.
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