Which of the following instruments and equipment must be sterilized before use in a microbiology laboratory?

• A. Graduated cylinder
• B. Inoculating loop
• C. pH meter
• D. Thermometer

Answer: (B)

Verified step by step guidance

1. Understand the concept of sterilization: Sterilization is the process of eliminating all forms of microbial life, including spores, from an object or surface. This is crucial in microbiology to prevent contamination of cultures and experiments.
2. Identify the function of each instrument: A graduated cylinder is used for measuring liquids, a pH meter measures acidity or alkalinity, a thermometer measures temperature, and an inoculating loop is used to transfer microorganisms.
3. Determine which instruments come into direct contact with microbial cultures: The inoculating loop directly touches microbial samples and culture media, making it a potential source of contamination if not sterilized.
4. Recognize that instruments like graduated cylinders, pH meters, and thermometers generally do not contact microbial cultures directly and therefore do not require sterilization before use, though they may need cleaning or calibration.
5. Conclude that the inoculating loop must be sterilized before use to ensure aseptic technique and prevent cross-contamination in microbiology experiments.