Synovial fluid culture and blood culture in acute arthritis. A multi-case report of 90 patients.

The use of blood culture methods for culture of synovial fluid (SF) has been suggested to increase the yield of microbes from SF of patients with septic arthritis. We report on a study of 94 SF cultures of 90 adult patients with acute effusions of the knee joint. Three different culture methods were used: conventional agar plate culture, culture with lysis and centrifugation (Isolator) and broth enrichment (BACTEC 6A and 7A). Blood was cultured simultaneously from 76 patients. In the patients with clinical septic arthritis, the SF cultures were positive by all the methods in 8 patients and negative by all the methods in 19 patients. The contamination rate of the SF cultures was 3/215 in the patients without clinical septic arthritis. We conclude that reliable evidence of septic arthritis is emerged from a SF culture by a single method, and that the choice of culture method is less critical. In addition, we discuss the role of blood cultures in the diagnosis of acute arthritides.