Diff mediasv

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differential media

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Diff mediasv

  1. 1. Biochemical Tests and Diagnostic Media• Labs #6 (white) and #7 (green) white• Overall scheme: Lab #6 (white) , last page white
  2. 2. SIM medium: Motility test POSITIVE: NEGATIVE:Organism moves Organism does NOTaway from stab move away from stab
  3. 3. SIM medium: Sulfur testH2S-NEGATIVE: H2S-POSITIVE: no black black precipitate precipitate formed formed
  4. 4. Simmon’s citrate agar slant negative positive
  5. 5. Diagnostic Media• Mannitol salt agar• Eosin methylene blue (EMB) agar• Brilliant green agar
  6. 6. Selective medium Selects for the GROWTH of some organisms and inhibits the growth of other organisms. i.e. Some organisms grow on a selective mediumwhereas others do not grow (or do not grow well) on that same medium.
  7. 7. Differential medium Differentiates between one type oforganism and another type of organism. Different types of organism look different from each other when grown on differential media.
  8. 8. Mannitol salt agarStaphylococcus Serratia aureus marcescens grows does not grow Selective medium High salt (NaCl) concentration in medium favors organisms that tolerate high salt concentration, e.g. Staphylococcus.
  9. 9. Mannitol salt agar Differential mediumDifferentiates among staphylococci
  10. 10. Mannitol salt agar Differential mediumDifferentiates among staphylococci
  11. 11. Mannitol salt agar Staphylococcus ferments mannitol (yellow) Differential mediumDifferentiates among staphylococci: • pathogenic Staphylococcus species ferment mannitol to produce acid (yellow medium)
  12. 12. Mannitol salt agar StaphylococcusMicrococcus does not ferments ferment mannitol mannitol (pink) (yellow) Differential medium Differentiates among staphylococci: • pathogenic Staphylococcus species ferment mannitol to produce acid (yellow medium) • less pathogenic Micrococcus (a staphylococcus)
  13. 13. Levine Eosin-Methylene Blue (EMB) Agar Gram negatives (growth) Gram positive(growth inhibited) SELECTIVE MEDIUM
  14. 14. Levine Eosin-Methylene Blue (EMB) AgarLactose Nonlactosefermenter fermenters DIFFERENTIAL MEDIUM
  15. 15. High acid producers on EMB e.g. E. coliblue-black colonies or metallic sheen
  16. 16. Levine Eosin-Methylene Blue (EMB) Agar Lactose fermenter Non-lactose fermenter (high acid producer: black colonies) Gram positive(growth inhibited) Lactose fermenter (low acid producer: pink colonies)
  17. 17. Brilliant Green Agar SELECTIVE • Growth of all gram positive and many gram negative bacteria inhibited • Growth of many Salmonella species occursDIFFERENTIAL
  18. 18. Brilliant Green Agar DIFFERENTIALDifferentiates lactose fermenters from nonlactose fermenters
  19. 19. Brilliant Green AgarLactose fermenter Non-lactose fermenter E. coli Salmonella
  20. 20. Catalase Test Many bacteria produce the enzyme catalase. catalaseH2O2 H2O + O2hydrogen oxygenperoxide (gas)
  21. 21. Catalase Test bubbles (gas)Catalase positive organism

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