Antiseptic/Disinfectant Disc Sensitivity Test:

The Disinfectant Sensitivity Disc Test is performed in a similar manner to the Kirby-Bauer Disc Diffusion Experiment.  In this case however, YOU make the discs! This disk diffusion test is a non- standardized protocol for determining the PRACTICAL antiseptic and disinfectant susceptibility of your particular unknown.

A pure culture of the UNKNOWN organism is inoculated on Mueller-Hinton agar. You must create a "lawn or confluent growth area" on the poured cooled agar using a sterile Q-tip dipped into your unknown organism.  Swab the entire surface of the agar quickly.  

The "disc" are place on this lawn BEFORE incubation.  Place the disc no closer than than 2 cm apart using flamed forceps or tweezers and press the discs into the agar gently. Then incubate the plate upside-down at the optimum temperature for 18 hours. 

To make the sterile filter-paper disks you obtain sterile filter paper punches and "dip" tem into your chosen test substances (at "use" concentration).  The treated filter discs are allowed to dry on a paper towel and then applied to the inoculated agar using sterile forceps are added to the plate (at a distance of no less than 2 cm apart).  The plate is then incubated upside-down at optimum temperature for 18 hrs.

After incubation the diameter of any  zone of inhibition is reported in millimeters. Results are reported as S (sensitive) or R (resistant).

See the Handbook page 113-1 (NO LONGER USED) for information on the Antiseptic/Disinfectant Disc Diffusion  Experiment...  USE ATLAS OR ONLINE!

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