I'm a food microbiologist here in Australia and was spending my (sad) day off googling around for more info regarding a current issue I am having in my lab.
We use XLD agar (Xylose lysine deoxycholate) for our Salmonella testing. As part of our Quality control for new batches coming in, we use a salmonella strain as the positive (no issues) and E.coli as the negative (For our testing, negative used is Citrobacter). Just wondering if anyone out there uses XLD and if you are finding that you are not getting the <G1+ growth (equivalent to <4 streaks of the 16 streaks). I am finding that I am getting above and in some cases full growth.
I've gone back to the manufacturer who have said they haven't had that issue..... even though we use the same strain of E.coli! Driving me crazy.
Comments from any professionals here would be much appreciated!