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20 Cards in this Set
- Front
- Back
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Why do we test public water |
To ensure the water is safe to drink (potable) and free from contamination with microbes |
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Coliform bacteria are |
Are gram-negative bacillus that ferment lactose |
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Types of coliform bacteria |
Eschericha, klebsiella, enterobacter |
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Water test determine |
The presence of coliform bacteria, which are great indicators for fecal contamination of water supplies |
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X-gal |
Is a chromogenic substrate that can be cleaved by an enzyme beta-galactosidase Turns media color blue-green |
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Mug |
Can be cleaved by an enzyme called beta-glucuronidase ( expresses by many E. Coli strains) Can be detected by UV light |
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EMB Stands for- |
Eosin methylene blue |
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Eosin Y |
is an indicator that reacts w/acid produced by lactose fermenters |
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Methylene blue |
Inhibits gram-+ growth |
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Hektoen enteric agar- HEA |
Detects presence of coliform Bile salts inhibit the growth of most gram-+ bacteria |
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MacConkey agar -MCA |
Detects coliforms Contains bile salts and crystal violet- which inhibit the growth of gram-+ bacteria |
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MacConkey agar |
Neutral red indicator dye turns pink when coliform are present No coliforms no color change |
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EMB color change |
Turns yellow-pinkish-orange with presences of coliforms Blue green w/ no coliforms |
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HEA |
Also has ferric ammonium citrate- turns black because it reacts with H2S gas |
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Staphylococcus |
Normal human microbiota Opportunist Catalase positive- express catalase. |
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Catalase |
Enzyme that decomposes hydrogen peroxide into water and oxygen |
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Catalase positive |
Oxygen bubbles form after mixing bacteria with peroxide - means they are a species of staphylococcus |
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Staphylococcus aureus |
Hemolytic on blood agar Halotolerant- grows on salt plates Ferments mannitol- sugar alcohol Produces coagulase enzyme - causes coagulation of blood plasma by converting fibrinogen to fibrin clot |
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Staphylococcus saprophyticus |
May be normal flora in vaginal tract and associated with UTI Halotolerant, generally ferments mannitol Coagulase negative |
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Staphylococcus epidermidis |
Common skin flora But may be associated w/nosocomial infections of blood Non-hemolytic on blood agar, halotolerant, doesn’t ferment mannitol and coagulase negative |
