Fighting a rising tide of MRSA infection in the young

July 1, 2005

The incidence of community-based methicillin-resistant Staphylococcus aureus (MRSA) infection in healthy children is increasing. This review discusses possible reasons for that rise, reviews antibiotic susceptibility patterns, and presents management guidelines.

Staphylococcus aureus causes a wide array of infections in children, from minor skin infections such as impetigo and furuncles (boils) to more serious conditions such as pneumonia, osteomyelitis, arthritis, endocarditis, and sepsis. The repeated emergence of resistance of S aureus (SA) against different antibiotics over time has driven development of new classes of antibiotics. The recent rise of community-based methicillin-resistant S aureus (MRSA) infections in healthy children and adults poses the latest challenge to managing these infections.

Antibiotic resistance by S aureus At its debut, penicillin was a powerful weapon against staphylococcal infections, and it remains the drug of choice for susceptible SA infections. However, penicillinase-producing strains appeared rapidly after the introduction of penicillin, and less than 5% of isolates currently retain susceptibility to that agent.1 These penicillinase-producing SA infections led to the introduction and widespread use of alternative antibiotics for treating staphylococcal infection. The semisynthetic penicillins (e.g., oxacillin, nafcillin) and the cephalosporins (e.g., cephalexin, cefuroxime) are not inactivated by the SA penicillinase, and the beta-lactamase inhibitor in beta-lactam/beta-lactamase inhibitor combinations (e.g., amoxicillin-clavulanate) inhibits the activity of the SA penicillinase. These types of antibiotics are, therefore, active against S aureus strains that are resistant to penicillin through penicillinase (or beta-lactamase) production. Bacterial protein synthesis inhibitors, such as clindamycin and macrolides, are unaffected by the presence of the penicillinase because of their distinct mechanism of action. Pediatricians have long used oral antibiotics such as cephalexin, erythromycin, amoxicillin-clavulanate, and clindamycin to treat outpatient SA infections and, similarly, oxacillin, cefazolin, and clindamycin to treat patients with SA infections who have been admitted to the hospital.