Comparison of BD Bactec Plus Aerobic/F medium to VersaTREK redox 1 blood culture medium for detection of Candida spp. in seeded blood culture specimens containing therapeutic levels of antifungal agents

Recovery of Candida spp. using the BD Bactec FX blood culture (BC) system (Bactec Plus Aerobic/F medium) and the VersaTREK system (aerobic Redox medium) was evaluated using seeded BC bottles with and without the addition of commonly used antifungal agents. BC bottles (n = 1,442) were each inoculated with 10 ml human whole blood and 0.1 ml of suspensions of Candida spp., with or without antifungal agents. BC bottles were incubated in the corresponding system for a maximum of 5 days. In the absence of antifungal agents, Bactec FX recovered 97.4% of Candida spp., and VersaTREK recovered 99.1% (P = 0.154). With regard to length of time to detection (LTD) and overall recovery, both systems had various levels of effectiveness in recovering C. glabrata. In bottles containing antifungal agents, Bactec FX recovered 83.1% of isolates, whereas VersaTREK recovered 50.7% of Candida spp. (P < 0.001). For BC bottles without the addition of antifungal agents, the median LTD for VersaTREK was 2.2 h faster than that of Bactec FX (P < 0.001). In the presence of antifungal agents, the Bactec FX recovery time was significantly faster than that of VersaTREK (median difference of 10.8 h, P < 0.001). We conclude that both systems have comparable abilities to recover Candida spp. from seeded blood cultures in the absence of antifungal agents. In the presence of therapeutic levels of commonly used antifungal agents, the Bactec FX system demonstrated a significantly greater recovery of various Candida spp., as well as a shorter LTD.