Group F Streptococcus. An unusual cause of arthritis.

Bacterial arthritis is a serious infection in children occurring either as the result of direct inoculation of organisms into the joint space, of spreading from a contiguous focus of infection, or of hematogenous seeding of the synovium. Although the etiologic agent can be identified in 60% to 70% of cases, joint fluid cultures may remain negative in a substantial number of patients. The most likely etiologic agent depends both on the route of infection and the age of the child. Overall Staphylococcus aureus, Hemophilus influenzae type b and streptococci are the leading causes of bacterial arthritis. Lancefield groups A, B, C, D, and G have all been implicated. However, septic arthritis due to hematogenous seeding with Group F Streptococcus has not been previously reported. A normal 10-month-old boy presented with acute monoarticular arthritis of the knee and had Group F Streptococcus isolated from the blood. Antimicrobial therapy resulted in complete resolution of the arthritis.