Repeat steps 1 to 6 as per quadrant streaking.If there is more than one colony type, each type should be streaked again on a separate plate to obtain a pure culture. All colonies should have the same general appearance. ![]() Examine the colonies grown on the plate carefully. The streaked plate is incubated at 37☌ for 24 hours. Note: Bi-plate inoculation of samples from sterile sites is often done in diagnostic laboratories to save time and space. Returning to the area you just streaked (area 3), extend the streaks into the center fourth of the plate (area 4). Flame the loop again and allow it to cool.Returning to the area you just streaked (area 2), extend the streaks into the third quarter of the plate (area 3). Returning to the edge of area 1 that you just streaked, extend the streaks into the second quarter of the plate (area 2). Immediately streak the inoculating loop gently over a quarter of the plate using a back-and-forth motion (see area 1 in the figure above).Pick an isolated colony from the agar plate culture and spread it over the first quadrant (approximately 1/4 of the plate) using close parallel streaks.Sterilize the inoculating loop in the bunsen burner by putting the loop into the flame until it is red hot or by incinerating it in a micro incinerator.Quadrant Streaking for isolation into pure culture Procedure Usually, by the third or fourth quadrant, only a few organisms are transferred, giving discrete colony-forming units (CFUs). There are four basic types of streaking methods Īs the original sample is diluted by streaking it over successive quadrants, the number of organisms decreases. Many different streaking patterns can be used to separate individual bacterial cells on the agar surface. To identify the organism: biochemical tests to identify bacteria are only valid when performed on pure cultures. ![]()
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