differential media

[Jim Rogers]

Fred & Rachel Brusseau <rbruss at ix.netcom.com> wrote in article
<35014CFB.7ECE70A3 at ix.netcom.com>...
> Basic Micro questions:

> MacConkey
> Does anyone know where I can find a picture of a coliform growing on
> MacConkey? (preferably on the net, but books are OK).

A good lab manual should have the color pictures you are looking for. 
Check a number of them in your library.

> Mannitol
> Can anyone confirm that Mannitol will turn yellow with pathogenic
> staphylococcus, but stay orange with EVERYTHING else?

Anything that ferments the mannitol and can grow in the high salt
concentration will turn MSA yellow.  I second the use of a catalase test
along with maybe a serum coagulation test.  Again, always run controls.

> Blood
> Is it true that ONLY beta hemolytic strep and pathogenic staphylococcus
> will form a clear ring on blood. 

Not true.  There are hemolytic Bacillus sp. out there too.  B cereus can be
found the soil and in cows with mastidis, which may not be a concern
depending on your source of milk.