"MacConkey (MAC) Media: Bile salts and crystal violet are added to inhibit gram-positives; the fermentation of lactose produces acidic products that turn the crystal violet (also a pH indicator) pink.\n\nEosin Methylene Blue (EMB) Media: Eosin blue and methylene blue inhibits the growth of gram-positives; the fermentation of lactose produces acidic products that turn the methylene blue to purple or creates a green metabolic sheen with high lactose fermentation.\n\nKligler’s Iron Agar (KIA)\n\nContents of media: (C) control, (1) glucose, (2) lactose, (3) peptone, (4A) phenol red, (4B) sodium thiosulfate, and (5) iron\n\nAll Enterobacteriaceae will initially ferment glucose, changing the color from red to yellow. If the microorganism can ferment lactose, it will be fermented second, also producing acid end products and the media will stay yellow. If lactose cannot be fermented, the peptone will be utilized and basic products will be produced, changing the slant back to red. The black color is ferrous sulfide produced from the reaction of H2S with the iron in the media."