When retrieving a sample from a culture tube with an inoculating loop, the cap of the tube is:

• A. discarded immediately after opening the tube
• B. removed and held in the hand to prevent contamination
• C. placed on the laboratory bench until sampling is complete
• D. left loosely attached to the tube during sampling

Answer: (B)

Verified step by step guidance

1. Understand the purpose of the inoculating loop technique: it is used to transfer microorganisms from a culture tube to another medium without contaminating the sample or the environment.
2. Recognize that contamination can occur if the tube cap is placed on an unsterile surface or discarded immediately, as this exposes the inside of the cap and the tube opening to potential contaminants.
3. Recall the proper aseptic technique: after opening the culture tube, the cap should be removed and held carefully in the hand to keep it sterile and prevent it from touching any surfaces.
4. Holding the cap in the hand also allows quick and safe replacement of the cap after sampling, minimizing exposure of the culture to airborne contaminants.
5. Therefore, the correct practice is to remove the cap and hold it in the hand during sampling, rather than discarding it, placing it on the bench, or leaving it loosely attached.