EDITORIAL

Resistant S aureus in the community:
Another of Nature's curveballs

Pediatricians in and around Chicago and Houston and in other parts of the country have been dealing with community-acquired methicillin-resistant Staphylococcus aureus (MRSA) for several years now. In Baltimore, we were caught off guard just this past spring and summer, when community pediatricians began reporting infections resistant to the antibiotics usually prescribed to treat them. Laboratory testing demonstrated that community-acquired MRSA had invaded our region.

Physicians who care for adults have been dealing with hospital-acquired strains of MRSA since the 1970s; in recent years, nosocomial MRSA infection has been a problem on pediatric units as well. Since the mid-1990s, pediatric infectious disease specialists and public health authorities in some areas of the country have reported MRSA as a cause of infection among children who were not hospitalized and had none of the usual risk factors for colonization or infection with such organisms. These strains have come to be called community-acquired MRSA, or CA-MRSA, to distinguish their epidemiologic characteristics and resistance pattern from those of nosocomial MRSA.

Unlike hospital-acquired strains, for which treatment with vancomycin is necessary, CA-MRSA strains are typically susceptible to gentamicin and trimethoprim-sulfamethoxazole (TMP-SMX). Some also remain susceptible to clindamycin, although special laboratory testing must be performed to ensure that clindamycin will be effective.

What are the recommendations for presumptive treatment of minor infection thought to be caused by S aureus? The answer depends on the local resistance rate. Careful wound care or a topical antimicrobial, or both, may be adequate for some infections. Initial antibiotic therapy with a ß-lactam antibiotic (a first-generation cephalosporin or dicloxacillin) continues to be appropriate where the resistance rate is low. Oral clindamycin or TMP-SMX has been used in areas where CA-MRSA is prevalent, but it is important to remember that streptococcal infection may not be adequately treated with TMP-SMX. For more serious infections that are likely caused by S aureus (pneumonia with empyema, osteomyelitis, endocarditis) initial therapy in regions where CA-MRSA is circulating should include intravenous vancomycin. Some of the newer fluoroquinolones are effective against CA-MRSA, but resistance to older members of this class has developed quickly, and fluoroquinolones remain restricted for pediatric patients (see "Fluoroquinolone use in children: Resistance and safety implications").

Those who provide medical care for children should be on the lookout for CA-MRSA. Bacterial culture and susceptibility testing are the best way to detect emergence of CA-MRSA in your area—particularly if an infection doesn't respond as expected to presumptive antimicrobial therapy. Local health authorities can help raise awareness of this pathogen among laboratories, emergency departments, and other acute care facilities, as well as among providers in primary care offices.

Just when we thought we were coming to terms with antibiotic resistance in virulent strains of Streptococcus pneumoniae, another common gram-positive pathogen is acquiring the ability to evade the usual antibiotic therapy that we provide.

Be careful out there!

Julia A. McMillan, MD, editor-in-chief of Contemporary Pediatrics, is professor of pediatrics, vice chair for pediatric education, and director of the residency training program, Johns Hopkins University School of Medicine, Baltimore.

Julia McMillan. Editorial: Resistant

S aureus

: Another of Nature's cu.

Contemporary Pediatrics

November 2003;20:10.