1. Place two small drops of water or saline on the surface of a clean glass slide.
2. Pick up a beta-lactamase disk with your forceps and place it in contact with one drop of fluid.
3. Repeat this procedure with a second disk, placing it on the second drop of fluid. Do not oversaturate the disks.
4. With your sterilized and cooled inoculating loop, pick up a portion of a B. subtilis colony and rub it across the surface of the first disk.
5. Rub a portion of a S. aureus colony across the surface of the second disk.
6. Observe the areas on the beta-lactamase disks where the organisms were inoculated for up to 30 minutes. A positive result is usually seen within 3 to 4 minutes.
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