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Homework Help: Gram negative bacteria and blood agar hemolysis

  1. Sep 9, 2007 #1
    I've looked all over and I can only find information on blood agar hemolyis for gram positive bacteria. Can I take this to mean that gram negative bacteria are generally gamma hemolytic? If so, are there any notable exceptions to this? One that I would guess is pathogenic E. coli, which cause hemolytic uremic (sp?) syndrome, but I was unable to find a direct connection to sheep's blood agar.
  2. jcsd
  3. Sep 10, 2007 #2


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    Haemolysis phenotypes are more frequently used to described Gram-positive rather than Gram-negative because the haemolysis phenotype is often crucial for proper identification of the Gram-positive especially the streptococci. However, haemolysis can be observed in Gram-negative.

    I've worked with a Gram-negative that was haemolytic but only with bovine blood. It didn't cause haemolysis in sheep's blood agar.

    If you do a search with E. coli and haemolysis
    or E. coli and hemolytic uremic syndrome on pubmed http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=escherichia coli haemolysis

    you may find the information you are looking for.
  4. Sep 10, 2007 #3
    I'm realizing now that mannitol salt agar is probabably an important to combine with sheep's blood agar. First if it grows on MSA you know it's probably Staphylococcus, then if it has beta hemolysis on the sheep's blood you know it's probably also pathogenic staph.
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