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Author7 Posts
  #1

Can anyone name some main differences between staph aureus and staph epidermidis(exclude catalse and coagulase)??




  #2

s.aureus:
B hemolysis + protein A on cell surface(an important virulance factor, inhibits complement activation)

s.epidermidis:
no hemolysis+no exotoxins(no food poisoning and tss)


  #3

When you all get to the point where you're reading culture reports, please be aware that Staph. epidermidis is usually included in the grouping reported as "coagulase negative Staphylococcus" nowadays.

An emerging pathogen in the CNS group is Staphylococcus lugdunensis. You can read more about this group on this very informative page:

http://www.postgradmed.com/issues/2001/10_01/eiff.htm

CNS is becoming recognized as a pathogen in many scenarios where it used to be considered skin flora. If you plan on going into infectious disease you may want to check out this page.


  #4

hi,Staph aureus can grow on MRS and ferment manitol but Staph epidermidis does not ferment manitol


  #5

we use ornithrine test in order to differentiate the Coagulase negative Staph (CONS) . whenever there is slightly lysed appearance on BA or no lysed at all, we will do the Dnase test, Coagulase, and ornithrine. especially from Blood culture, all CONS must report even it is commented as possible contamination. Staph lugdunensis already submitted as pathogen Staph in our hospital. so we have to differentiate CONS by ornithrine which only Staph.lugdunensis positive an negative for Staph.epidermidis and others Staph. there is one thing i m wondering about Micrococcus spp, is it true Micrococcus spp are OXIDASE POSITIVE. or only a few type of strain that show its Oxidase Positive? and are there any other Micrococcus spp that not yellow colony as we always found?


  #6

Oxidase testing is only used for gram negative organisms. A "modified oxidase" test (Microdase discs) are used on gram positive, catalase positive organisms only. Micrococcus are Microdase positive.

At our lab, if a CONS is found in one out of two SETS of blood cultures, we consider it a contaminant unless the doctor insists on workup. If CONS is found in two or more sets (or one set if only one is drawn) we do an ID on the Staph and a sensitivity. We use the GP card in the Vitek2 for identification. We were using PYR discs and setting up GP cards only on PYR positive Staphs, but for epidemiological reasons we started running the full ID on Staphs from blood cultures and other sterile body fluids.

BTW, effark84, the test is ORNITHINE smiling face Not sure if you're running a rapid ornithine disk or incubating tubed ornithine overnight. The GP cards are quite easy. There are also other methods for Staph identification.

It is important that the CONS's are identified correctly, as there are different MIC breakpoints for SLUG than for other CONS's.


  #7

well, these are rlly helpful. modified oxidase i c. i will suggest this to our boss. the best answer i got. thanks. for the ornitrine, we only have incubated type. rapid are quite expensive since the "upper" people says that we are not a research lab.. LOl. what can we do.. but it is really important to identify the correct type of Staph. thats for sure. thank you so much. i will look forward for more of these matter.nod





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