unknown: s. aureus vs s. epidermidis

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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thuydeebird
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unknown: s. aureus vs s. epidermidis

Post by thuydeebird » Sat Apr 21, 2012 1:39 am

I'm currently taking Microbiology and I am working on my unknown. I have narrowed down my unknown to S. Aureus and S. Epidermidis. I suspect that it is S. Aureus because my MSA plate turn yellow after incubation. However, when I did a coagulase test, it resulted in a gelatin like substance (not solid or liquid). Since it is not completely solid, I can't say that it is positive. This contradict my MSA plate because S. Aureus is coagulase positive. I'm not sure what test to believe. I have only done the coagulase test once and I have done the MSA test multiple time. I have picture of my MSA and TSA plate.

Is there anyone who can help me clear this up?

I also have picture of my MSA plate and TSA plate.

JorgeLobo
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Re: unknown: s. aureus vs s. epidermidis

Post by JorgeLobo » Sat Apr 21, 2012 11:18 am

Repeat coagulase and use + and - controls.

KIJRA
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Unknown: S.aureus or S. epidermidis

Post by KIJRA » Sat Apr 21, 2012 6:24 pm

Any clotting, even if it looks like gel, will be a positive result.

JorgeLobo
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Re: unknown: s. aureus vs s. epidermidis

Post by JorgeLobo » Sun Apr 22, 2012 12:04 pm

Repeat the test with controls. You should expect the appropriate reaction.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC187014/

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