Inoculating a Petri Dish Procedure for Dry and Wet Swab

Label Divide the Petri dish into sections-if applicable-and label the bottom (agar side) of the dish using permanent marker Label along the outer edges of the dish so the labels do not interfere with viewing the organisms

Inoculate Use sterile cotton swab to wipe the surface or liquid being tested. Do not let anything touch the sterile tip If you use a control plate, new untouched, cotton swabs are good to use

For a Dry Surface Wet the swab by dipping to in sterile water. Then wring out by wiping it against the inside of the container If the swab is too wet, the liquid will flow into other sections and microbial colonies will run into each other. Swab the dry surface

For a Liquid Dip sterile swab into liquid and wipe it against the inside of the container Inoculate the nutrient agar using a back and forth motion covering the entire area of the section or plate. Do not swab to close to dividing lines for the next section

Tape Place cover on inoculated Petri dish and seal with parafilm-narrow strip, stretched around outside edge of covered dish Can use masking tape as well-just make sure it is sealed-dangerous bacteria! Incubator set at 95 º