Certification Board for Sterile Processing and Distribution (CBSPD) Sterile Processing Technician Practice Exam 2025 - Free Sterile Processing Technician Practice Questions and Study Guide

Gram-positive microorganisms stain blue or purple due to their thick peptidoglycan cell wall. During the Gram staining procedure, the crystal violet dye is applied first, which penetrates the thick peptidoglycan layer and stains the cells. Following this, iodine is used as a mordant to help fix the dye. When a decolorizer is applied, it affects Gram-negative organisms more than Gram-positive ones because of the latter's robust cell wall structure that retains the dye. Consequently, Gram-positive bacteria do not lose the crystal violet and thus appear blue or purple under a microscope after the staining process is complete.

In contrast, Gram-negative bacteria, which have a thinner peptidoglycan layer surrounded by an outer membrane, will lose the crystal violet during decolorization and instead take up a counterstain, resulting in a red or pink appearance. This distinction is crucial for microbiologists to identify and differentiate between types of bacteria in clinical settings.