Streak Plate Technique

Streak swab of sample over one quarter of the sterile Petri dish in a back-and-forth "tornado" pattern. This is quadrant #1.Discard swab in biohazard bag. Sterilize loop in flame of Bunsen burner.Allow loop to cool without waving it about. Place loop on next quadrant of Petri dish, next to quadrant #1. Gently drag the loop into quadrant #1 a few times, to obtain just a bit of bacteria from that first sample, then spread that material over quadrant #2, in another tornado pattern.Again sterilize loop in flame of Bunsen burner or hub of microincinerator, and allow loop to cool.Place loop in next quadrant of Petri dish, adjacent to quadrant #2. Gently drag the loop into quadrant #2 a few times, to obtain just a bit of bacteria from that sample, then spread that material over quadrant #3 in a tornado pattern.Again sterilize loop in flame of Bunsen burner and allow loop to cool.Place loop in next quadrant of Petri dish, adjacent to quadrant #3. Gently drag the loop into quadrant #3 a few times, to obtain just a bit of bacteria from that sample, then spread that material over quadrant #4, in a back-and-forth "tornado" pattern.Make sure that the quadrant #4 streak does not touch the quadrant #1 streak.Incubate plate at 37 degrees C for at least 24 hours. When attempting to isolate a specific type of bacteria from a sample, this streak plate technique will need be repeated, possibly several times, in order to obtain a pure sample.