What is the purpose of fixing a smear before Gram staining?

• A. To fix the cells to the slide
• B. To adhere cells to the slide and kill bacteria to reduce biosafety risk.
• C. To stain the cells
• D. To rinse the slide

Answer: (B)

Fixing a smear before Gram staining serves to keep the sample in place and to inactivate the organisms for safety. This step adheres cells to the slide so they don’t wash away during the stains, and it kills the bacteria, reducing biosafety risk. It also helps preserve cell morphology during the staining process, preventing distortion from autolysis or movement. Without fixation, cells can be washed off and live bacteria pose a handling risk, while fixation itself is not the staining step.