microbio practical 2 tests

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zzto
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271568
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microbio practical 2 tests
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2014-04-22 23:48:52
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bio practical tests
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microbio practical 2 tests
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  1. DMM medium
    • If there is a mutation in an amino
    • acid biosynthetic pathway gene, the bacteria cannot grow on DMM.
  2. TSA plate
    • TSA contains amino acids and can save a 
    • mutant via supplementation
  3. Plain LB plate
    contains no antibiotics
  4. Salmonella-Shigella (SS) Agar
    • Selective--- contains bile salts and brilliant green to inhibit Gram positive bacteria and most Gram negative bacilli
    • Differential---Lactose/ neutral red -
    • if ferment, form red colonies; not, colorless colonies
    • Sodium thiosulfate/ Ferric citrate -
    • colonies with black center are positive for H2S production
  5. MSA --- Mannitol salt agar
    • Selective for halophilic
    • bacteria--- staphylococcal spp.

    • Differential --- ferment mannitol à
    • eg. Staphylococcal aureus
    • do not ferment mannitol
    • eg. Staphylococcal epidermidis
  6. EMB--- Eosin Methylene Blue agar plates
    Selective--- Eosin and methylene blue inhibit the growth of Gram positive bacteria.

    • Differential--- lactose
    • fermentation (yes, pink; no, colorless
    • colonies) ---strong acid production
    • produces ‘greenish
    • metallic sheen’.
  7. Staphylococcus aureus
    • differentiated
    • from other Staphylococcal
    • skin flora based upon its ability of mannitol fermentation and
    • hemolysis.
  8. Blood agar medium
    used to detect (strongest to weakest) B, a, or y hemolysis
  9. Brain Heart Infusion plate:
    • BHI is a rich medium commonly used for the
    • isolation of fungi and bacteria
  10. staph catalase and coagulase
    • Catalase test---
    • Staphylococcal spp.
    • positive

    • Coagulase test ---
    • Staphylococcal aureus coagulase
    • positive
  11. Why is mannitol salt agar used as a selective medium for normal skin flora?
    • MSA selects for halophilic bacteria,
    • and salt resistant bacteria can be found on the skin’s surface
  12. Mitis-Salivarius Agar
    • Crystal violet---inhibit most G+ bacteria except streptococcus
    • Potassium tellurite---inhibit
    • G- bacilli
    • strep salivarius will produce gum-drops while strep mitis will make small,flat, light blue colonies
    • Enterococcus will make dark black blue colonies
  13. Is blood agar selective or differential? Explain
    • It is actually an enriched medium,
    • as most all bacterial species can grow upon blood agar. It could be considered
    • differential based upon hemolysin production, but it is not selective.
  14. What is one test that can be quickly used to differentiate between Staphylococci
    and Streptococci
    spp.?
    catalase
  15. MacConkey Agar
    • used to isolate gram negative organisms, at the same time differentiate organisms
    • according to their lactose fermentation ability.
  16. Bile esculin agar
    commonly used to identify members of the genus Enterococcus (E faecalis and E. faecium).

    • ---Bile inhibits the growth of other Gram +
    • ---Sodium azide inhibits Gram –
    • ---Differentiates the ability to hydrolyze esculin

    many organisms hydrolyze esculin, but only Enterococcus spp. can do so in the presence of bile.
  17. urea broth inoculations
    • differential for urease production 
    • pink=positive
  18. Countable plate numbers
    • spread plates are countable if they fall between 25 – 250 isolated colonies. 
    • for the spot plate dilutions you would look for spots with at least 10 colonies and
    • no more than 30 colonies.

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