The IRB-BART initially has an immediate reaction of a brown color at the bottom of the tube, then the brown color disappears leaving the solution yellow and no slime present. How should this be interpreted?
IRB-BART initially has an immediate reaction to a brown color
This immediate reaction to a brown color at the bottom of the tube, followed by the brown color disappearing over the next few days is a phase one reaction which does not designate bacterial activity (see Standard Methods for BART Testing on www.dbi.ca). In this case the initial brown color in the base is triggered by the movement of ferric ions out of the base medium. Over time these ions disperse into the liquid medium as a yellow color.