Which of the following actions could be a source of cross-contamination in a laboratory setting?

• A. Labeling all samples before starting an experiment
• B. Using the same pipette for different samples without sterilization
• C. Autoclaving glassware before use
• D. Wearing gloves while handling sterile equipment

Answer: (B)

Verified step by step guidance

1. Understand the concept of cross-contamination: it occurs when microorganisms or substances are unintentionally transferred from one sample or environment to another, potentially compromising the integrity of experiments.
2. Evaluate each action in terms of whether it could transfer contaminants between samples or surfaces.
3. Labeling all samples before starting an experiment is a good practice to avoid mix-ups and does not cause cross-contamination.
4. Using the same pipette for different samples without sterilization can transfer microorganisms or substances from one sample to another, making it a potential source of cross-contamination.
5. Autoclaving glassware before use sterilizes it, preventing contamination rather than causing it, and wearing gloves while handling sterile equipment helps maintain sterility and reduces contamination risk.