Highest 'Practical' Agar Concentration - Results

mamber mamber at synapse.bms.com
Thu Mar 2 11:35:40 EST 1995


I wanted to determine if increasing the agar concentration of microbiological
media would have any effect on the diffusion rates of a variety of 
antimicrobial substances used in agar diffusion assays.  Accordingly, I made 
media with 1.5%, 2%, 2.5% and 3% agar and used either Micrococcus luteus 
or Bacillus subtilis as an assay organism.  I tested a variety of standard 
antimicrobial/cytotoxic agents in agar diffusion assays, including 
actinomycin D, kanamycin, mitomycin C and tetracycline.  Essentially no 
differences in inhibition zone diameters were obtained.  Thus, I must 
conclude that high agar concentrations have minimal, if any, effects on 
slowing the diffusion of antimicrobial agents in agar diffusion assays.  
If anyone disagrees with these findings, I would be interested in hearing 
from them.  SWM

mamber at synapse.bms.com

PS Media with agar concentrations above 3% were too difficult to work with.



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