In streak plate technique, which instrument is used to streak the sample?

• A. A loop is used to streak the mixed sample over the surface of a solid culture medium
• B. A pipette is used to pipette liquid
• C. A spread rod
• D. A swab

Answer: (A)

The main concept here is that the streak plate technique uses an inoculating loop to place and dilute the sample across the surface of a solid culture medium, allowing isolation of individual colonies. The loop—often a fine wire that can be sterilized by flame and cooled before use—picks up a small amount of sample and is dragged in a pattern across the agar to progressively dilute the cells. A pipette is for transferring liquids, not for creating the streak pattern on solid media. A spread rod is used for spreading liquid evenly in a spread plate, not for the quadrant streak approach. A swab is mainly for collecting samples or transferring them in some methods, but the standard streak method relies on the loop to achieve separation of colonies.