Need Help With Experiment

KM mirza at eskimo.com
Tue Apr 23 12:09:06 EST 1996

On Wed, 17 Apr 1996, David R. Boone wrote:

> Terry J. Peek wrote:
> > I am trying to differentiate between Serratia marcescens and a gram pos. cocci
> > that I suspect is Staph epidermidis or S. aureus. I've placed the culture on
> > 10% NaCl agar. I'll check the results later this morning. What is the best way
> > to seperate these organisms using the resources of a small college lab? Is my
> > first step in the right direction? Any suggestions would be appreciated.
> > Thanks.       Terry
> Terry,
> There are lots of differences between Serratia marcescens and the two cocci you 
> mentioned.  If you know an organism is one of these three species, it is 
> relatively easy to distinguish Serratia marcescens.  Many strains of Serratia 
> marcescens when grown as surface colonies produce a red pigment (in contrast, 
> Staphylococcus epidermidis is usually light colored and Staphylococcus aureus is 
> usually dark yellow or golden (the species epithet refers to gold).  The color of 
> colonies is really not very taxonomically significant (in fact, <90% of Serratia 
> marcescens strains produce the red pigment), but if you want a quick and dirty 
> discriminator, this may be it.  From a taxonomic standpoint, probably the most 
> reliable differentiating characteristics are morphological: Serratia are 
> gram-negative rods, whereas staphylococci are gram-positive cocci, often arranged 
> in grape-like clusters.
> -- 
> David R. Boone
> Professor of Environmental Microbiology
> Oregon Graduate Institute, Portland
> 503-690-1146
> boone at ese.ogi.edu
> http://www.ese.ogi.edu/ese_docs/boone.html
I am puzzled at the 90% of S.marcescens and production of pigment.
Prof.Boone where is that reference, my understanding of pig production was
a lot smaller than 90%.

May be in the envoirnment isolates are differeent, I am a clinical  man,
my observation of clinical isolates is a lot different.
Hope to hear ur reply.

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