My supervisor has noticed when acid is produced on MacConkey with MUG
agar, no fluorescence is found - even with a control inoculum of E.coli.
If NaOH is added on top of the agar, and then placed under UV light again,
the fluorescence is visible. We have not found a statement to this affect
on our media, or in literature from companies selling media. When the
lactose is taken out of the media, apparently no acid is produced, giving
a good positive result. We have also found this problem with Lauryl
Sulfate Broth with MUG as well. Has anyone else found this to be true?
Is it documented in literature anywhere?