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Lactose fermenters turn red or pink on MacConkey agar, and nonfermenters do not change color. The media inhibits growth of gram-positive organisms with crystal violet and bile salts, allowing for the selection and isolation of gram-negative bacteria. The media detects lactose fermentation by enteric bacteria with the pH indicator neutral red. [2]
enterocolitica strains can be identified through the use of stool samples being grown on MacConkey plates and Yersinia Selective Agar. The MacConkey plates employ the fact that Y. enterocolitica is non-lactose fermenting, and therefore show up on the plates as 2mm translucent pale colonies. On Yersinia Selective Agar plates Y.
Proteus vulgaris is a rod-shaped, nitrate-reducing, indole-positive and catalase-positive, hydrogen sulfide-producing, Gram-negative bacterium that inhabits the intestinal tracts of humans and animals. It can be found in soil, water, and fecal matter.
Proteus is a genus of Gram-negative bacteria. It is a rod shaped, aerobic and motile bacteria, which is able to migrate across surfaces due its “swarming” characteristic in temperatures between 20 and 37 °C. [1] Their size generally ranges from 0.4 to 0.8 μm in diameter and 1.0–3.0 μm in length. They tend to have an ammonia smell. [2]
Most strains of Acinetobacter, except some of the A. lwoffii strain, grow well on MacConkey agar (without salt). Although officially classified as not lactose-fermenting, they are often partially lactose-fermenting when grown on MacConkey agar. They are oxidase-negative, catalase-positive, indole-negative, nonmotile, and usually nitrate-negative.
They are aerobic, catalase positive, urease positive, nonsporeformers. They grow on MacConkey agar, but do not ferment the lactose. Burkholderia gladioli can be distinguished from the other Burkholderia because it is oxidase negative [1] B. gladioli is indole negative, nitrate negative, and lysine decarboxylation negative. [13]
Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium.It appears as a mucoid lactose fermenter on MacConkey agar.
MacConkey agar is a selective and differential medium used to differentiate between gram-negative bacteria while inhibiting the growth of gram-positive bacteria. Adding bile salts and crystal violet to the agar inhibits the growth of most gram-positive bacteria, making MacConkey agar selective.