Assuming you are referring to disc diffusion testing might this not be an
effect of a diffusion gradient which is maximum at the surface and decreases
with increasing depth? David Post
Stephen W Mamber wrote in message <3A8DA3FA.471A9384 at bms.com>...
>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
>appreciated.
>>Thank you,
>>Stephen Mamber, Ph.D
>Bristol-Myers Squibb
>
