Effects of delayed-entry conditions on the recovery and detection of microorganisms from BacT/ALERT and BACTEC blood culture bottles.

Manufacturers generally recommend that blood culture bottles be loaded into instruments within a short time of collection. However, in our experience, delays often occur prior to loading the bottles. We examined the effect of holding bottles under various temperatures (T)-room temperature (RT), 4 degrees C, 37 degrees C, and RT for 2 h following incubation at 37 degrees C (to simulate transit [TR])-and for various holding times of 4, 12, and 24 h. We utilized the BacT/ALERT system with FA and FN bottles and the BACTEC system with Plus (PL) and Lytic 10 (LY) bottles. Standardized inocula and 5 ml of blood were added to each bottle. Fifteen organisms were evaluated based upon expected performance: aerobic (FA and PL), anaerobic (FN and LY 10), and facultative (all bottles). Based upon expected performance, the FA and FN bottles recovered 458 of 468 organisms and 282 of 288 organisms, respectively, whereas the PL and LY bottles recovered 453 of 468 organisms and 257 of 288 organisms, respectively (P = <0.001, FN versus LY). There were 3, 11, 21, and 27 false-negative results for bottles held at 4 degrees C, RT, 37 degrees C, and TR, respectively. There were 4, 8, and 50 false-negative results for bottles held for 4, 12, and 24 h, respectively. Our results support holding these four bottle types at 4 degrees C or at RT for up to 24 h and at 37 degrees C for up to 12 h. We propose that manufacturers only need to make claims for "delayed entry" when these bottles are held for more than 24 h at 4 degrees C or at RT or for more than 12 h at 37 degrees C.