FIGURE 3.

Incubation time required to reach O.D._{630 nm} = 0.1 following SST-IMS isolation of F. tularensis LVS from blood cultures. F. tularensis LVS blood cultures at initial concentrations ranging from 2.4 × 10³ CFU/ml to 2.7 × 10⁹ CFU/ml were subjected to the SST-IMS procedure. A 100-μl aliquot of the SST-IMS outputs from each blood culture was plated in 6 replicate in a 96-well microtiter plate. The microtiter plates were incubated in a plate reader for 48 h at 37°C in ambient air, and the absorbance at O.D._{630 nm} was read at 1-h intervals until reaching 0.1 (see dotted line), representing mid-log growth phase. The linear regression of log concentration versus time yielded the following prediction equation: Time (h) = -5 × log (CFU/ml) + 46.