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DrHeasley FHeasley at CHEMISTRY.COM
Wed Apr 10 13:07:55 EST 1996

At 05:26 PM 4/10/96 +0100, vigfrid.ness at veths.no (Vigfrid Ness) wrote:
>Is there a quick method to determine if a culture of  Staphylococci consists
>of both catalase positive and negative organism. If the culture is catalase
>negative then there is no Staph. aureus present, but what I want is an
>equally simple methode to determine if there is no catalase negative
>organisms present.
>Can anyone help me????
>Vigfrid Ness

There are catalase negative organisms present in virtually all
staphylococcal cultures, because there are spontaneous mutants present in
all of them.  The issue is whether the number of catalase negative forms is

If you're concerned about a significant percentage, then you can make a good
streak plate and test the separated colonies as usual with peroxide,
observing carefully whether there are colonies that do not exhibit
characteristic signs.

If you are concerned with extremely low numbers (like 1 in 10^6) then you
will need to use a selection process to separate and enrich for them.

Frank Heasley, Ph.D.

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