Which of the following is the best method to prevent air contamination when using an inoculating loop during microbiological procedures?

• A. Cool the loop by waving it in the air
• B. Dip the loop in alcohol before use
• C. Wipe the loop with a dry paper towel
• D. Flame the loop until red-hot before and after use

Answer: (D)

Verified step by step guidance

1. Understand the purpose of sterilizing an inoculating loop: it is to eliminate any microorganisms present on the loop to prevent contamination of the culture and the environment.
2. Evaluate each option based on its effectiveness in sterilization: waving the loop in the air does not generate enough heat to kill microbes; dipping in alcohol may reduce microbes but does not guarantee complete sterilization; wiping with a dry paper towel only removes visible debris but does not sterilize.
3. Recognize that flaming the loop until red-hot is a standard microbiological technique that uses high heat to effectively kill all microorganisms on the loop surface.
4. Note that flaming before use prevents introducing contaminants into the culture, and flaming after use prevents spreading microbes to the environment or other samples.
5. Conclude that the best method to prevent air contamination when using an inoculating loop is to flame it until red-hot before and after use, ensuring complete sterilization.