Superior Detection of Pathogens in Synovial Fluid by the Bactec 9240 Peds Plus/F System Compared to the Conventional Agar-based Culture Method

ABSTRACT

To improve culture yield in cases of possible septic arthritis; we compared culture of joint fluid aspirates on conventional agar-based media to culture in Bactec 9240 Peds/Plus F blood culture bottles with and without the addition of fastidious organism supplement (FOS). Over a period of 21 months; we analysed 123 synovial fluid samples and isolated 20 pathogens. The Bactec methods proved superior by yielding more pathogens than the conventional culture method (p=0.074). However; this method also yielded more contaminants within the first three days of incubation (p=0.027). All contaminants detected after three days of incubation were the result of overgrowth on conventional method agar plates. The Bactec methods provided clinicians with a positive pathogen result one day earlier than the conventional counterpart (p=0.001). Four isolates of Neisseria gonorrhoeae were only cultured with the Bactec method. No significant benefit was demonstrated by supplementing blood culture bottles with FOS. We recommend that whenever infection by fastidious organisms is suspected; synovial fluid aspirates should be cultured using automated blood culture systems to increase the culture yield and to decrease the time to detection