Tampons shouldn't be worn overnight because... 1  Tampons need to be changed every 4-6 hours and many people sleep longer than this - changing often is important as tampons allow bacterial growth while preventing vaginal cleaning so the longer a tampon is worn the more bacteria can multiply within the vagina.
MacConkey agar is a selective medium containing bile salts and crystal violet that inhibits the growth of Gram-positive bacteria while allowing for the growth of Gram-negative bacteria.MacConkey agar is often used when investigating and culturing fecal bacteria.he MacConkey agar we talked about as an example of a selective media is also a differential media. In addition to the selective bile salts and crystal violet, MacConkey agar contains a pH indicator and the sugar lactose.
Selective media: Selective media allows the growth of certain type of organisms, while inhibiting the growth of other organisms. This selectivity is achieved in several ways.