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list the gram reaction and morphology of th enteric bacteria
Gram+poor growth or no growth, organism is inhibited by crystal violet and/or bile
Gram-Good growth, organism is not inhibited by crystal violet or bile
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The selective agent for MacConkey Agar
bile salts and crystal violet and Ferric ammonium citrate
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indicators for MacConkey Agar
neutral red
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Basis for differentation for MacConkey Agar
lactose
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Basis for differentation for MacConkey Agar
lactose
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MacConkey Agar inhibits the growth of Gram ____ bacteria
positive
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MacConkey Agar supports the growth of Gram ____ bacteria
negative
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Probable coliform
pink to red growth with or w/o bile precipitate, organism produces acid from lactose fermentation
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Noncoliform
growth is "colorless" (not red or pink), organism does not ferment lactose. No reaction
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MacConkey Agar has ____ numer of sugars
one
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Selective media
suppresses growth of unwanted bacteria and encourages growth of desired microbes.
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Differential media
facilitates distinguishing the desired microbe from others in a mixed sample
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Enterobacteriaceae
family name; includes gram (-) organisms found in human GI tract.
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Enterics
general term for the enterobacteriaceae family members.
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Fecal Coliforms
are a commonly used bacterial indicator of sanitary quality of foods and water
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Lactose
a disaccharide composed of glucose + galactose
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Enteric lactose fermenters (LF) such as E. coli , Enterobacter, and Klebsiella are Less pathogenic or more pathogenic?
They are less pathogenic ( Non pathogenic)
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Non-Lactose Fermenters like Salmonella, Shigella, Proteus are Less pathogenic or more pathogenic?
They are more pathogenic
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Mention the organisms that are Lactose Fermenters
E. coli, Enterobacter, Klebsiella pneumoniae
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Mention the organisms that are Non-Lactose fermenters.
Salmonella, Shigella, Proteus, Morganella morganii
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Mention the three types of agar used to identify gram (-) microbes
MacConkey AgarEosin Methylene Blue agar (EMB)Hektoen Enteric agar (HE/SS)
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MacConkey agar is
both selective and differential
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MacConkey agar "selects" for ..
- Gram (-)- suppresses growth of gram (+)- Crystal violet and bile salts inhibit growth of gram (+) due to inhibition of cell wallpeptidoglycan synthesis.
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In MacConkey agar " Crystal violet and bile salts" inhibit the growth of gram (+) due to
Crystal violet and bile salts" inhibit the growth of gram (+) due to ....inhibition of cell wall peptidoglycan synthesis.
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MacConkey agar "differentiates" between
lactose fermenters and non-lactose fermenters- Lactose provides the sugar substrate for fermentation- Neutral red dye is a pH indicator which turns red when acidic and is colorless when basic.
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In MacConkey agar "end products of lactose fermentation increase acidity of media and turns pH indicator what color?
Red
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Results of MacConkey agar
- Gram (+) will not grow on this media- Lactose fermenters grow pink/red-Non-lactose fermenters grow colorless colonies
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