BSCI 424 — PATHOGENIC MICROBIOLOGY — Fall 2000

Handling Agar Plates

Do not remove the lid unnecessarily or for prolonged periods of time. Do not lay the lid down on the counter or put the bottom of the Petri dish into the inverted lid. While inoculating the agar plate, you may either:

        Set the covered plate upside down on the counter. When you are ready to inoculate it with the loop, lift the bottom half (with the media in it), and hold it up vertically for a moment while streaking it. Replace it into the lid while re-flaming the loop. Lift bottom again to continue streaking, etc.

        Set the plate right side up on the counter. Lift the lid slightly ajar and hold it at an angle, while you are streaking the plate. While this prevents contaminated dust from falling on plate, it may be difficult to see what you are doing.

Note: Method No. 1 is recommended for examining a plate which has been incubated in an inverted position. Otherwise, water may condense on the lid and drip down onto the medium, causing the colonies to coalesce.

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