What may look like an infected bug bite on your child's arm, could be methicillin-resistant Staphylococcus aureus, or MRSA. The staph infection is increasingly seen in communities across the nation that is resistant to antibiotics most commonly used to treat skin infections.

Researchers reported in the Aug. 17 issue of The New England Journal of Medicine that MRSA is the most common cause of skin and soft-tissue infections among patients presenting in emergency rooms across the country. MRSA is resistant to the antibiotics used for years to treat these skin conditions, such as cephalexin and dicloxacillin.

"The study points to the rising prevalence of this type of MRSA and the need for clinicians to culture infections and make sure the proper antibiotic is administered to treat MRSA," said Dr. Jane Siegel, an infectious diseases expert on the medical staff at Children's Medical Center Dallas.

Antibiotic resistance
Since the 1960s, MRSA has been found in healthcare settings, generally among patients who have been hospitalized or are in nursing homes. In the last few years, however, a new type of MRSA has emerged, affecting people with no connection to healthcare settings. The study demonstrates that the infections appear to be common in people who are not connected to any particular risk group.

Community-associated MRSA most often manifests itself on the skin as a boil or pimple that can be swollen, red and painful, and have discharge.

Researchers cultured the acute skin or soft-tissue infections of 422 patients seen at 11 metropolitan emergency rooms in the United States during August 2004. Out of those patients, 249, or 59 percent, were found to have MRSA. The proportion of infections caused by MRSA in various cities ranged from 15 to 74 percent. Further characterization of the MRSA samples, performed at the Centers for Disease Control and Prevention, revealed that one genetic type accounted for 97 percent of the samples.

Researchers tested the antibiotic resistance of the isolated MRSA samples and found that in 57 percent of cases, doctors had prescribed an antibiotic to which the bacteria were resistant.

"Doctors need to change what they've done for decades, since traditional antibiotics don't work against MRSA," Dr. Siegel said. "We encourage physicians to reconsider antibiotic choices for skin and soft-tissue infections in areas where MRSA is prevalent in the community."

Dr. Siegel notes that most MRSA cases are mild, and having the infection drained and keeping it clean resolves the problem. But when antibiotics are needed, it's important to prescribe an effective medication. Sometimes these infections may require hospitalization and, in rare cases, may even be life-threatening.

Researchers tested the effectiveness of different types of antibiotics on the MRSA samples and found that 95 percent were susceptible to clindamycin, 6 percent to erythromycin, 60 percent to fluoroquinolones, 100 percent to rifampin and trimethoprim-sulfamethoxazole and 92 percent to tetracycline.

The next step, according to Dr. Siegel, is to compare these different antibiotics in real patients in order to identify an optimal treatment.

Risk factors
The study revealed several potential risk factors for community-associated MRSA. Patients with MRSA were more likely to report a spider bite as the reason for the skin lesion, perhaps thinking it was a bite in absence of other skin problems. Those with MRSA also were more likely to have close contact with a person with a similar infection.

"However, none of these risk factors were consistent enough to help doctors identify cases of MRSA - it appears now that everyone is at risk," Dr. Siegel said. "So if you think you have a spider bite or other type of skin lesion that is not healing, you want to see your doctor to make sure it's not an infection like MRSA."

Tips for avoiding transmission
Dr. Siegel notes the importance of educating patients in order to avoid transmission. She offers the following guidance:

• Wash hands often with soap and water to keep them clean, or use an alcohol-based hand sanitizer (if hands are not visibly soiled).
• Don't share towels, razors or other personal items.
• Avoid contact with other people's wounds or bandages.
• Keep breaks in your skin clean and covered and watch for signs of infection, such as redness, warmth and swelling.
• See your doctor if you notice signs of infection; don't try to drain a boil yourself at home.
• If you have a skin infection, keep the infected area covered with a clean, dry bandage until it is healed; wash your hands thoroughly after changing the bandage and put used bandages in the trash.

For more information, please visit the Centers for Disease Control and Prevention Web site or log onto www.childrens.com.