this MacConkey with crystal violet can grow enterococcus
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Enterococcus faecalis typically does not grow on MacConkey agar as this selective and differential medium is primarily used for isolating and differentiating members of the Enterobacteriaceae family, which are mostly gram-negative bacteria. Enterococcus species are gram-positive bacteria and do not ferment lactose, the key ingredient in MacConkey agar that allows for differentiation.
MacConkey agar is designed to grow Gram-negative bacteria and also contains crystal violet dye which inhibits the growth of Gram-positive bacteria. Since S. aureus is Gram-positive it should not grow on MacConkey agar. No. MacConkey agar inhibits MOST of the Gram-positive bacteria. There are some Gram-positive bacteria that can tolerate bile-salt are able to grow in MacConkey agar. Enterococcus and some species of Staphylococcus are able to grow in MacConkey. (lack citation though)
E. coli that grow on MacConkey agar typically exhibit lactose fermentation, causing them to produce pink or red colonies. These colonies may also appear mucoid due to the production of a polysaccharide capsule. Additionally, E. coli on MacConkey agar will typically not grow well under acidic conditions, as the agar contains crystal violet which inhibits the growth of Gram-positive bacteria.
Lactococcus lactis is a bacteria commonly used in the production of dairy products like cheese and yogurt, while Enterococcus faecalis is a bacteria that is often found in the intestines of animals and humans. L. lactis is generally considered safe, whereas E. faecalis can be a pathogen and cause infections in humans, particularly in hospital settings. Additionally, L. lactis is a lactic acid bacterium used in fermentation processes, while E. faecalis is a member of the Enterococcus genus known for its ability to survive in harsh environments.
This type of agar is designed to grow gram-negative bacteria. It will not grow gram-positive bacteria due to a dye in the formula of the agar.
Most gram positive bacteria do not grow on MacConkey agar or Eosin Methylene Blue (EMB) agar, as these are selective media designed to inhibit the growth of gram positive organisms. So, typically, you would not expect a gram positive bacteria to grow on these media.