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The organism on the right produced no color, so it does not appear to be a lactose fermenter. MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation. [1]
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.
Acinetobacter is a genus of Gram-negative bacteria belonging to the wider class of Gammaproteobacteria. Acinetobacter species are oxidase-negative, exhibit twitching motility, [7] and occur in pairs under magnification. They are important soil organisms, where they contribute to the mineralization of, for example, aromatic compounds.
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.
English: MacConkey agar is a selective and differential medium used to isolate and differentiate Gram-negative bacteria, particularly those belonging to the family Enterobacteriaceae. It's primarily used to distinguish between lactose-fermenting (LF) and non-lactose-fermenting (NLF) colonies.
Eikenella corrodens is a pleomorphic bacillus that sometimes appears coccobacillary and typically creates a depression (or "pit") in the agar on which it is growing. Only half produce the pitting of the agar considered characteristic. [citation needed] It is a slow-growing, facultative anaerobe and a gram-negative bacillus. [6]
MacConkey agar is culture medium designed to grow Gram-negative bacteria and stain them for lactose fermentation. It contains bile salts (to inhibit most Gram-positive bacteria), crystal violet dye (which also inhibits certain Gram-positive bacteria), neutral red dye (which stains microbes fermenting lactose), lactose and peptone.
Traditionally, MacConkey agar has been used to distinguish those bacteria that ferment lactose from those that do not. This is important because gut bacteria, such as Escherichia coli , can typically ferment lactose, while important gut pathogens, such as Salmonella enterica and most shigellas are unable to ferment lactose.