Differentiation Help

neufeld at paprican.ca neufeld at paprican.ca
Mon Mar 1 18:03:48 EST 1999

Sometimes it is difficult to tell whether the cells are very-short rods or
cocci.  One tip that might help: when you are looking at a Gram +'ve cocci,
there is typically very little doubt that they are cocci (e.g. Staphylococcus
or Streptococcus).  If there is some doubt about whether it is a cocci or a
rod, then it often turns out to be a rod.  Also, if you are looking at a G-
stain in a micro intro lab then it is likely a rod since G- cocci are almost
all nasty pathogens and would not have been given to you to examine.
Hope this helps,

In article <7be4u1$nh at sjx-ixn6.ix.netcom.com>,
  "Mike" <maj at unforgettable.com.nospam> wrote:
> I'm a university student in a microbio intro course and we're working with
> unknowns.  Many in the class, including myself, are having a difficult time
> differentiating between rods and cocci on student-prepared Gram stain slides
> at 1000X oil-immersion magnification.  Often they look like rods but also
> dividing cocci.  The little "bugs" are just so small.
> Any tips for the beginner?
> Thanks in advance for your help!
> Mike

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