Methicillin revelation

Phillip San Miguel pmiguel at
Thu Jun 24 13:13:49 EST 1999

"Dr. Duncan Clark" wrote:

> [...]
> But where are you getting your methicillin from? It was withdrawn by
> Sigma two years or so ago because of, I believe, world wide concerns
> over MRSA etc. and was no longer being prescribed and therefore
> manufacture was also stopped.

Yeah, that's the explanation I'd thought up too.  But it is not correct.
Check out:
There, "Mike" tells us:

"Many staphyloccal strains are now methicillin-resistant, which generally
means the strain is no longer
sensitive to any of the penicllinase-resistant penicllins and to the
cephalosporins. Methicillin is no longer used in the medical community, at
least in Boston, and this probably explains its scarcity -- it is no longer
commercially viable."

He then suggested oxacillin or nafcillin might work similarly.  I think
they probably do, but a few days ago was the first time I ever tried them.
Thus I have not tested this hypothesis.

We still have a bottle of methicillin from about 3 or 4 years ago.  My
point was that neither methicillin nor oxacillin nor nafcillin were
effective against DH5alpha at 100 ug/ml concentration in plates.  However
adding ampicillin at 20 ug/ml does completely restrict the growth of
DH5alpha.  Maybe amp 20 ug/ml would work fine by itself.  I didn't test
this, but I guess it would.  Sorry my experiment was designed to test
something else and was not ideal for answering this question.  Next time I
do a transformation with a pUC (or similar) vector, I'll test out the
satellite restricting capabilities of at least oxacillin + amp compared to
amp alone.

> Do you get satellites with Oxacillin or Nafcillin and do you mix with
> Ampicillin or use as is?
> [...]

Oxacillin or Nafcillin, alone, do not prevent the growth of (untransformed)
DH5alpha.  But with the addition of ampicillin DH5alpha will not grow.

I guess my original post has expired.  You can see it at:

Phillip San Miguel
Purdue Genomics Center

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