Objectives: To determine whether time-to-positivity (TTP) in aerobic and anaerobic blood culture vials is useful to predict the presence of Candida glabrata in patients with candidaemia.
Methods: TTP was recorded for both aerobic and anaerobic vials for each blood culture set of monomicrobial candidaemia. We considered TTP as the shortest time registered for any positive vial. Two diagnostic criteria were evaluated: the cut-off TTP value as obtained from a receiver operating characteristic curve and the detection of growth only or with a shorter TTP in anaerobic vials.
Results: A total of 157 episodes were analysed of which 19 (12.1%) were due to C. glabrata. The TTP for C. glabrata was longer than that for other species. C. glabrata grew more frequently than other species in anaerobic vials [9/19 (47%) versus 19/138 (14%); P = 0.001] and also more often exclusively or earlier in anaerobic vials [7/19 (37%) versus 5/138 (4%); P < 0.0001]. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of a TTP >56.5 h for predicting the presence of C. glabrata were 47%, 88%, 36% and 92%, respectively. Growth detection only or earlier in anaerobic flasks had a sensitivity of 37%, a specificity of 96%, a PPV of 58% and an NPV of 92%.
Conclusions: Using the BACTEC 9240 system, a TTP ≤ 56.5 h is useful to rule out C. glabrata. In addition, in settings with an ~12% prevalence of C. glabrata candidaemia, yeast detection exclusively or earlier in anaerobic vials increases the probability of the presence of C. glabrata to 58%, which may be useful for early treatment optimization.
Keywords: bloodstream infections; culture media; time to blood culture positivity.