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Nonpathogenic Lactose Fermenters (name 3)
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E. coli, Enterobacter. Klebsiella
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Nonpathogenic Lactose Non-fermenters (name 1)
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Proteus
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Pathogenic Lactose Non-fermenters (name 2)
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Salmonella, Shigella
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 Oxidase test. Direct method used on Pseudomonas aeruginosa and Escherichia coli. Which is the positive result and which is the negative? |
 Pseudomonas: Positive with a purple/blue color change. Escherichia: Negative with no color change. |
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Pseudomonads are obligate aerobes and use an electron transport (or oxidation-phosphorylation) system that includes an enzyme called....
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Cytochrome c oxidase
(Cytochrome c oxidase picks up electrons and passes them to a pigment called cytochrome c, which is part of the electron transport pigment system needed for aerobic respiration. This oxidase reagent acts as a false electron donor so if Cytochrome c oxidase is present, it will take the electrons from the oxidase reagent. When the reagent becomes oxidized, by giving away the electrons, it turns purple.) |
 Lactose fermentation tests using Phenol red lactose broth (PR lactose broth) used on Escherichia coli and Salmonella typhimurium. |
 Escherichia coli: Positive with yellow (acidic) coloration; Positive for gas production. Salmonella typhimurium: Negative with orange/red (neutral) coloration; Negative for gas production. |
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Phenol red shifts (pH and coloration)
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Alkaline pH -------> cerise pink
Neutral pH --------> red (when lactose is present) Acidic pH ----------> yellow (positive) Remember: Most enterics are Lactose fermenters (LF) while potential pathogens will be Lactose nonfermenters (LNF). |
 Lactose fermentation and bile salt tolerance using MacConkey's Agar (MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA). On MAC, anything that grows is..... |
Bile salt/dye tolerant
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 Lactose fermentation and bile salt tolerance using MacConkey's Agar (MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA). On MAC, any growth that is pink or pinkish is a ...... |
Lactose Fermenter (LF)
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 Lactose fermentation and bile salt tolerance using MacConkey's Agar (MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA). On MAC, any growth that is clear or colorless is a ...... |
Lactose nonfermenter (LNF).
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 Lactose fermentation and bile salt tolerance using MacConkey's Agar (MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA). On EMB, anything that grows is..... |
Dye tolerant
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 Lactose fermentation and bile salt tolerance using MacConkey's Agar (MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA). On EMB, any growth that is dark purple or purplish is a ....... |
Lactose fermenter
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 Lactose fermentation and bile salt tolerance using MacConkey's Agar (MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA). On EMB, any growth that is transparent is a ........ |
Lactose nonfermenter
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Lactose fermentation and bile salt tolerance using MacConkey's Agar
(MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA).
On HEA, anything that grows is ..... |
Bile salt/dye tolerant
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Lactose fermentation and bile salt tolerance using MacConkey's Agar
(MAC), Eosin Methylene Blue Agar (EMB), and Hektoen Enteric Agar (HEA).
On HEA, any growth that is bright orange to salmon pink is a ...... |
Lactose fermenter
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