Used as basal medium for microbiological assay of antibiotics.
Principles and uses
Antibiotic Medium Nº 2 is the standard agar base used for the microbiological assay of antibiotics in pharmaceutical preparations, body fluids, animal
feed preparations and other materials.
The activity (potency) of an antibiotic can be demonstrated under suitable conditions by its inhibitory effect on microorganisms. Reduction in antimicrobial
activity may reveal changes not demonstrated by chemical methods. The antibiotic media are identified numerically with names assigned by Grove and
Randall in “Assay methods of antibiotics”. The use of standardized culture media and strict control of all test conditions are essential requirements in the
microbiological assay of antibiotics in order to obtain satisfactory test results.
This medium has the same formula as Antibiotic Medium Nº 5 (Cat. 1524) and Antibiotic Medium Nº 8 (Cat. 1004), with the difference that the pH of the
medium has been adjusted to 6,6. To carry out the antibiotic test, the Antibiotic Medium should be prepared on the same day as the test is done. The
sample can be tested by the two methods of dilution and assay plate diffusion.
Gelatin peptone and beef extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is source of vitamins,
particularly the B-group. Bacteriological Agar is the solidifying agent.
Formula in g/L
Bacteriological agar 15 Beef extract 1,5
Gelatin peptone 6 Yeast extract 3
Quality control
Solubility w/o rest
Appareance Fine powder
Color of the dehydrated medium Cream
Color of the prepared medium Amber, sligtly opalescent
Final pH (25ºC) 6,6±0,1
