Test for catalase

Fergus McClelland redux at perdrix.demon.co.uk
Mon Mar 15 22:10:17 EST 1999


Judy/Bob Dilworth <dilworth at megsinet.net> wrote:

>Staphylococci are not gram positive diplococci. Streptococci,
>specifically pneumococci, or Streptococcus pneumoniae, are gram positive
>lancet shaped diplococci that are catalase negative, as are all
>streptococci.  Staphylococci, which are gram positive cocci in clusters,
>are catalase positive.  This test is usually done by taking a small
>applicator stick and smearing some of the colony onto a glass slide and
>adding a drop of 3% peroxide, the kind you buy in a drug store.  If it
>is positive, you will see bubbles immediately.  This test will not tell
>you what species of Staphylococcus you have.  You must do a coagulase
>test for that, or use a latex agglutination test like Staphaurex. 
>Staphylococcus aureus is catalase positive and coagulase positive. 

Is there a simple coagulase test - like the catalase test above? 
>
>My other concern is that, if you have a prostatic secretion, Neisseria
>gonorrhoeae can be under-decolorized and look like gram positive
>diplococci. They should be gram negative diplococci - like two beans
>paired together.  Neisseria gonorrhoeae is catalase positive, but it is
>also oxidase positive.  Oxidase testing is not done on strep or staph,
>as this test is only done on gram negative bacteria.  Neisseria
>gonorrhoeae usually only grows on chocolate or Thayer-Martin (or Martin
>Lewis, depending upon which formulation your lab uses) but I have seen
>some grow on blood plates.  It looks nothing like Staph. on a plate,
>though.  Staphylococci, whether coagulase positive or negative, are
>yellowish white to white to grayish white.  Neisseria look tan on
>chocolate and/or TM and are sticky.  If they appear at all on Blood
>agar, they are clear and sticky and not at all white.

The patient has been tested by his local hospital STD clinic, and all
tests were negative - though the examining doctor did see "some clumps
of Gram positive inflammatory bacteria" in the urine sample he gave,
which did not get commented on by the lab.

The bateria do form into groups mostly, though there were many pairs
as well before he was given two courses of Augmentin a year or so ago.
They certainly look like the pictures I have seen of Staph Aureaus on
the Web, and the sample I got from a German manufacturer of sample
slides. The patient has been celebate for many years. The condition
started about 4 years ago.

>
>Make sure what you're working with.

Thank you once again, Judy, for your detailed reply.
>
>Judy Dilworth, M.T. (ASCP)
>Microbiology
>
>Fergus McClelland wrote:
>
>> >
>> If I want to test a sample of expressed prostatic secretion which is
>> heavily laden with what looks like a Staph, (Gram + diplococci) and
>> want to know if it is catalase +ive or -ive, what would be the
>> quickest and simplest way please?




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