Formulation of Medium Used Smaller Amount of Carbohydrate

Suppose you innoculate a PR broth with a slow-growing fermenter. After 48 hours, you see slight turbidity but score it as (-/-). Is this result a false positive or a false negative? Is this a result of roor specificity or poor sensitivity of the test system?

Early formulations of this medium used a smaller amount of carbohydrate and occasionally prodused false alkaline (pink) result after 48 hours. Why do you think this happened? List at least two steps, as a microbiologist, that you could take to prevent the problem.