Clinical comparison of an agar slide blood culture bottle with tryptic soy broth and a conventional blood culture bottle with supplemented peptone broth.

The Roche Septi-Chek biphasic blood culture system with tryptic soy broth was compared with a conventional blood culture bottle with supplemented peptone broth in 6,956 paired blood cultures from adult patients. Both systems were inoculated with equal volumes of blood (5 ml) and incubated aerobically (vented) for 2 weeks. More clinically important bacteria and fungi, including Staphylococcus aureus, S. epidermidis, Escherichia coli and other Enterobacteriaceae, Pseudomonas aeruginosa, and Candida albicans and C. tropicalis were recovered from the biphasic system (P less than 0.001). In contrast, more clinically important anaerobic bacteria (P less than 0.001) and Gardnerella vaginalis (P less than 0.05) were recovered in conventional supplemented peptone broth. Staphylococci (P less than 0.01), Enterobacteriaceae other than E. coli (P less than 0.05), and fungi (P less than 0.001) were detected 1 or more days earlier in the biphasic system, whereas streptococci (P less than 0.001) were detected earlier in the conventional bottle. The overall superiority of the agar slide blood culture system compared with conventional blood culture bottles was confirmed by this evaluation. For optimal detection of anaerobic bacteremia, however, the agar slide bottle should be paired with an anaerobic bottle.