Is S. Marcescens on of my unknowns!!!( it is making me crazy)

  1. Yesterday was the dreaded day of Micro unknowns!!! I streaked my broth on a TSA plate and it grew colonies with little pink dots in them. Some people in the class said S. Marcescens, but I thought it S. Marcescens looked like bright red colonies that blanket the plate! Has anyone seen it like this ( white with the pink dots in the middle)? PLease Help ME!!!!! I hate this part of the class! I am soooooooo confused!
    Thanks-Tara
    ****Oh, I don't know if this is any help, but I incubated it a 37 degrees Celcius
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  2. 11 Comments

  3. by   EmeraldNYL
    Did you do a gram stain?
  4. by   ucandoit
    yep, gram negative rods!
  5. by   Berta
    What other test did you do and what were the results? You may need more testing. I had to do over 15 before I could even begin to narrow mine down. Berta
  6. by   zacarias
    gram negative rods sounds dangerous LOL
  7. by   prmenrs
    And, they are!
  8. by   ucandoit
    I streaked it on a Mackonkeys Agar plate and it was a positive growth/ mixed fermenter! My instructor says that S. Marcescens is the only one, out of all the gram negative rods. But, I don't know if there is a backup test to run, just to be sure! Anyone know of one?
  9. by   essarge
    I got S. Marcescens for my unknown. The first thing I did was look up red colonies on the computer and there was a picture of it!!! I got ten extra points for knowing it before we started any testing.

    Try searching the internet for more hints on SM, it helped me a lot!!
  10. by   LauraLou
    There are lots of tests you can do to confirm your id of S. marcescens.

    Indole- negative
    Citrate- positive
    Lactose- negative
    Hydrogen Sulfide- negative
    Voges-Proskauer- positive
    Oxygen requirements- facultative anaerobe
    Motility- motile
  11. by   ucandoit
    Thanks guys I have got to go to lab tomorrow and do a Blood agar plate on the other unknown, Strep, and I have ran all the others on the s. marcescens but tehy keep coming out wrong. The lab assistant said that there is too much water condenstion in all the plates! Pray for me!!!!-Tara
    P.S.-Thanks again for all the advice!!!
  12. by   colleen10
    Sorry I can't give you much more advice than what has allready been said.

    If it's any consolation, in my Micro class no two slides of the same microbe looked alike!!!
  13. by   Nurse Ratched
    I know it's driving you nuts now, but I really loved micro. Like a great mystery story trying to figure that stuff out. Good luck!

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