So here is the deal, same use different recipies different results to do the same thing. I'll just post some lecture notes and hope that helps:
The conclusion drawn if no growth appeared on MacConkey agar and EMB agar after inoculation of the media and an incubation period could be the bacteria used was possibly a Gram positive non-enteric sample.
Gram-negative bacteria that do not grow on MacConkey agar and Eosin Methylene Blue agar include: Helicobacter pylori Neisseria gonorrhoeae Haemophilus influenzae
Eosin methylene blue (EMB) agar is selective for gram-negative bacteria, especially those that can ferment lactose. Common bacteria that grow on EMB agar include Escherichia coli and Enterobacter aerogenes. These bacteria are differentiated by their ability to ferment lactose, producing colonies that are metallic green or dark purple on EMB agar.
Pseudomonas aeruginosa can grow on Emb agar, as it is a selective and differential growth medium commonly used to isolate and differentiate members of the Enterobacteriaceae family, including P. aeruginosa. Its growth on Emb agar will exhibit the characteristic green metallic sheen due to its ability to produce pyocyanin pigment.
Staphylococcus bacteria typically do not grow well on Eosin Methylene Blue (EMB) agar. EMB agar is selective for gram-negative bacteria, particularly Enterobacteriaceae, and contains dyes that inhibit the growth of gram-positive bacteria like Staphylococcus.
The conclusion drawn if no growth appeared on MacConkey agar and EMB agar after inoculation of the media and an incubation period could be the bacteria used was possibly a Gram positive non-enteric sample.
The conclusion drawn if no growth appeared on MacConkey agar and EMB agar after inoculation of the media and an incubation period could be the bacteria used was possibly a Gram positive non-enteric sample.
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.
On nutrient agar, Yersinia appears as smooth, opaque colonies with a pale yellowish color. On EMB agar, colonies may show greenish metallic sheen due to lactose fermentation. On MacConkey agar, Yersinia typically forms colorless to pale pink colonies due to its inability to ferment lactose.
Gram-negative bacteria that do not grow on MacConkey agar and Eosin Methylene Blue agar include: Helicobacter pylori Neisseria gonorrhoeae Haemophilus influenzae
Mycobacterium phlei is a non-fastidious organism that is commonly found in soil and water. It is not commonly grown on Eosin Methylene Blue (EMB) agar, as EMB agar is more selective for gram-negative enteric bacteria. Instead, Mycobacterium phlei is typically cultured on media specifically designed for mycobacteria, such as Middlebrook agar or Lowenstein-Jensen agar.
Eosin methylene blue (EMB) agar is selective for gram-negative bacteria, especially those that can ferment lactose. Common bacteria that grow on EMB agar include Escherichia coli and Enterobacter aerogenes. These bacteria are differentiated by their ability to ferment lactose, producing colonies that are metallic green or dark purple on EMB agar.
E.coliIn stool samples microscopy will show Gram negative rods, with no particular cell arrangement. Then, either MacConkey agar or EMB agar (or both) are inoculated with the stool. On MacConkey agar, deep red colonies are produced as the organism is lactose positive, and fermentation of this sugar will cause the medium's pH to drop, leading to darkening of the medium. Growth on Levine EMB agar produces black colonies with greenish-black metallic sheen. This is diagnosic of E. coli.SalmonellaCulture is microbial growth on or in a nutritional solid or liquid medium; increased numbers of organisms simplify identification. Culture also facilitates testing of antimicrobial susceptibility.Communication with the laboratory is essential. Although most specimens are placed on general purpose media (eg, blood or chocolate agar), some pathogens require inclusion of specific nutrients and inhibitors or other special conditions
EMB Agar
The peptones in EMB agar provide nitrogen for bacterial growth, while the lactose is a source of carbon. These ingredients support the growth of certain coliform bacteria, which ferment lactose to produce characteristic color changes on the agar.
MacConkey's agar is a selective growth media that is best suited for isolation of coliform bacteria. This bacterial is red and is gram negative. The agar plate inhibits the growth of gram positive organisms and allows gram negative organisms to grow.
Pseudomonas aeruginosa can grow on Emb agar, as it is a selective and differential growth medium commonly used to isolate and differentiate members of the Enterobacteriaceae family, including P. aeruginosa. Its growth on Emb agar will exhibit the characteristic green metallic sheen due to its ability to produce pyocyanin pigment.