Proposed algorithm may not apply to other centers

Dr. Kocher and colleagues should be applauded for attempting to help guide empiric antibiotic treatment for acute hematogenous osteomyelitis before culture results become available. The small number of patients with MRSA infections (8 percent) included in this paper, however, makes the applicability of these data to other centers questionable.

Sheldon L. Kaplan, MD, chief of the infectious diseases service at Texas Children’s Hospital (TCH) in Houston, has prospectively tracked every S aureus infection admitted to TCH since Aug. 1, 2001. Over a 6-year period, 57 percent of the 225 cases of acute hematogenous osteomyelitis at TCH were caused by MRSA.

Dr. Kaplan looked at several of the variables that Dr. Kocher found were predictive of a MRSA infection and found no relationship between them and the antibiotic sensitivity of the organism. Instead, his team has discovered that other factors seem to be more important.

Genetic analysis of the isolates at TCH has shown that patients with S aureus strains harboring the gene encoding for the exotoxin Panton-Valentin leukocidin (PVL) had significantly higher measures of inflammation—including serum white blood cells, CRP, and erythrocyte sedimentation rates—during hospitalization. Patients infected with PVL-positive strains also had more complex infections and more frequent complications such as deep venous thrombosis and chronic osteomyelitis irrespective of the methicillin-sensitivity of the isolate. In fact, Dr. Kaplan’s group found that the percentage of MSSA infections that caused invasive disease such as osteomyelitis was significantly higher than the percentage of MRSA infections that led to a deep infection.

Analysis for the presence of PVL raises interesting questions about the virulence of some S aureus strains, but, unfortunately, has no clinical use at this time. In areas such as Houston, where MRSA infections are more common, surgeons should prescribe empiric antibiotic therapy based on the burden of MRSA in the community and the prevalence of clindamycin-resistant strains.

Disclosure information: Dr. Epps—Pediatric Orthopaedic Society of North America, AAOS Now.

Howard R. Epps, MD, is a member of the Fondren Orthopedic Group, LLP, and a member of the AAOS Now editorial board. He can be reached at epps@fondren.com

References:

1. Hulten K, Kaplan S, Gonzalez BE, et al: Three-year surveillance of communithy onset health care-associated Staphylococcus aureus infections in children. Pediatr Infect Dis J 2006;25(4):349-353.
2. Miller LG, Kaplan SL: Staphylococcus aureus: A community pathogen. Infect Dis Clin North Am 2009;23(1):35-52.