Tuesday, February 7, 2012

FYP in My Style: Disc Diffusion

Disc diffusion is a method to determine sample antimicrobiotic strength by looking at the zone of inhibition. Okay lets get it started!
McFarland standard should match with bacterial broth absorbent reading which determined by using UV-Vis spectrophotometry. After that you can proceed with disc diffusion.

Pipette 100 micro-lite of bacterial broth onto agar and spread with hockey-stick.
Pipette 10 micro-lite of sample on blank disc and put on agar.
Incubate 18 hours for bacteria and 72 hours for fungi.

1. Make sure you're doing it in laminar floor to avoid any contamination but if the laminar floor is not available, you can doing it in open space but nearby Bunsen burner and with several common precautions like wearing mask and glove, turn off the fan and aircond, last but not least make sure the table is wiped with 70% Ethanol before and after the experiment.
2. You can always divided you agar in four sections. Three for the sample's triplicate and one for negative control. Negative control should be in every plate so you can compare it with your sample.
3. Do your positive control in different plate is an advantage if you're doing this experiment in group as it only need one agar plate for positive control thus, reducing the agar plate usage.
4. Aseptic technique is required to maintain the sterility.

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