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

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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!: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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Did you do a gram stain?

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yep, gram negative rods!

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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

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Specializes in tele, stepdown/PCU, med/surg.

gram negative rods sounds dangerous LOL

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Specializes in NICU, Infection Control.

And, they are!

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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?

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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!!

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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

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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!!!

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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!!!

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Specializes in Geriatrics/Oncology/Psych/College Health.

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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