Page 11 - Quality control of pharmaceuticals (07-PA 704) practical

Practical work:

Number the cups in agar (1, 2, 3, and 4).
Number the test tubes (the tube containing the agent takes number 1 while the empty tubes take
2, 3 and 4).
Transfer 2 mL sterile diluent in each of the last 3 test tubes.
Transfer 2 mL from tube 1 to tube 4 by serial dilution (2 fold serial dilution).
N.B.MIC determination is always done by 2 fold serial dilution.
Fill the cups with the corresponding solutions using “Pasteur pipette” (2-3 drops depending on
the height of the cup, but the number of drops is the same in each cup).
Dropping of the unknown concentration in the corresponding cup (u).

N.B.
-Start with the lowest concentration (= highest dilution) i.e. 4, 3, 2 then 1, so that the higher
concentration doesn’t interfere with the lower one.
-Wash the Pasteur pipette with a certain volume of the required concentration before filling a
new dilution for saturation of the glass with the antimicrobial agent then reject the washing, after
that fill again and drop in the corresponding cup.
-The size of the cup differs from plate to another and even within one plate (if the agar is slightly
slanted) therefore choose the most shallow cup as cup number 4 to avoid overfilling of cups then
use the same number of drops in each cup.

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