Advice offered for empirically treating osteomyelitis in the CA-MRSA era

Remaining up-to-date with prevalent Staphylococcus aureus isolates within a given community, performing blood cultures, monitoring C-reactive protein levels and utilizing magnetic resonance imaging were among techniques for managing osteomyelitis that John S. Bradley, MD discussed at the Pediatric Academic Societies Annual Meeting held in Baltimore this weekend.

MRSA prevalence varies from around 40% to as high as 80% in areas across the United States, often making disease severity difficult to predict, according to Bradley, who leads the division of infectious diseases at Rady Children’s Hospital in San Diego.

“Subperiosteal abscess, adjacent and distal soft tissue abscesses and septic thromboembolic phenomenon are associated with clinical courses of osteomyelitis caused by CA-MRSA,” Bradley said. “These kids require greater amounts of surgery and clearly have prolonged hospitalization.”

In areas where MRSA prevalence is high, he recommended including coverage for resistant isolates even before positive cultures are obtained due to the potential for severe illness. He suggested beginning therapy with a beta-lactam such as nafcillin, to assure coverage against methicillin-susceptible S. aureus isolates, plus vancomycin for children who present with severe clinical symptoms. Clindamycin is typically used for patients with more mild symptoms.

When culture results are available, physicians should switch to the appropriate definitive therapy. However, Bradley recommended oral clindamycin as the primary step-down, convalescent long-term therapy if MRSA is prevalent in the community even if the culture returns negative, when the infection “looks, walks and smells like MRSA.”

MRIs remain the gold standard in imaging for detecting multiple sites of infection, as the technology enables physicians to detect bone and soft tissue inflammation simultaneously.

C-reactive protein levels should be monitored regularly to determine the duration of intravenous antibiotic therapy. “During the past four to five years we’ve been sending kids home on oral therapy once their C-reactive protein levels drop to around two or three, because by that point it seems as though they are no longer in danger of needing additional surgery,” Bradley said.

Optimal antibiotic therapy durations have yet to be established, but can range from about six to 10 weeks, according to Bradley.

“We are only beginning to understand the natural history of this organism,” he said. “We need prospective, controlled data on children with osteomyelitis with both old and new antibiotics to define the safety and efficacy for this particular disease.” –by Nicole Blazek

For more information:

Bradley JS. #3065. Pediatric Academic Societies Annual Meeting; Baltimore; May 2-5, 2009.