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2011-02-14 16:39:49
micro lab quiz

micro lab quiz 2/15
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  1. Phenylethyl alcohol agar
    • encourages gram positive growth
    • inhibit by phenytylethyl alcohol= gram negative
  2. Mannitol Salts Agar
    • poor or no growth= inhibited by NaCl= not staph
    • good growth= organism is not inhibited by NaCl= staph
    • Yellow growth or halo= produces acid from mannitol rementation= possible pathogenic S. Aureus
    • Red growth (no halo)= doesn't ferment mannitol. no reaction
  3. MacConkey Agar
    • poor growth= inhibited by crystal violet/bile
    • good growth= not inhibited by crystal violet/bile= gram -
    • pink to red w/ or without preciptate= produces acid from lactose fermentation= possible coliform
    • growth is colorless= doesn't ferment lactose. no reaction= noncoliform
  4. Eosin Methylene Blue Agar
    • poor growth= organismm inhibted= gram +
    • good growth= not inhibited= gram -
    • pink and mucoid= ferments lactose w/ little acid production= possible coliform
    • "dark" (purple to black, w/ or w/o green metallic sheen)= ferments lactose and/or sucrose w/ acid production= porobably coliform
    • Colorless (no pink, purple, or metallic sheen)= doesn't ferment lactose or sucrose= noncoliform
  5. Hektoen Enteric Agar
    • poor growth= inhibited by bile= gram +
    • good growth= no inhibited= gram -
    • pink to orange= produces acid from lactose fermentation= not shigella or salmonella
    • blue-green w/ black precipitate= doens't ferment lactose, but reduces sulfer to hydrogen= possible salmonella
    • blue green growht w/o precipitate: doesn't ferment lactose or reduce sulfur= possible shigella or salmonella
  6. Xylose Lysine Desoxycholate Agar
    • poor growth= inhibited by desoxycholate= gram +
    • good growth= not inhibited= gram -
    • growth is yellow= organism produces acid= not shigella or providencia
    • red growth w/ black center= reduces sulfur to hydrogen sulfide= not shigell or providencia
    • Red growth w/o black center= organism does not ferment xylose or ferments xylose slowly= probable shigella or providencia