Help re:"Coning" Phenomenon Within Agar Inhibition Zone Edges

Stephen W Mamber Stephen.Mamber at
Fri Feb 16 17:04:42 EST 2001

Can anyone give me some literature references, or perhaps a
remedy, with respect to a phenomenon I refer to as "coning"?  My
description of the phenomenon is as follows:  Certain antibiotics
yield a sharp zone edge with a given organism, but within the
zone, growth (partial growth) seems to increase as it extends
into the agar.  It appears to be like looking down at an ice
cream cone with the bottom cut off (which would be the area of
complete inhibition).  My explanation for this is that decreased
oxygen content makes the organism less sensitive to the compound,
on the assumption that there is more exposure to oxygen at the
surface of the agar than at the bottom.  I'm sure others have
seen this, so any help regarding this phenomenon would be greatly

Thank you,

Stephen Mamber, Ph.D
Bristol-Myers Squibb

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