Which feature best distinguishes ethanol (70%) from glutaraldehyde as a disinfectant?

## Comparison: Ethanol (70%) vs Glutaraldehyde ### Key Differences | Feature | Ethanol (70%) | Glutaraldehyde | |---------|---------------|----------------| | **Speed of action** | Rapid (seconds–minutes) | Slow (3–10 hours for spores) | | **Sporicidal** | No (bacteriostatic only) | Yes (high-level disinfectant) | | **Contact time** | Very short | Very long | | **Best use** | Skin antisepsis, rapid surface disinfection | Instrument disinfection, endoscopes | | **Toxicity** | Irritant, flammable | Toxic vapours, requires ventilation | | **Environmental use** | Suitable | Not suitable (toxic) | **Key Point:** The fundamental distinction is **contact time and sporicidal activity**. Glutaraldehyde is a high-level disinfectant that kills spores but requires prolonged immersion (3–10 hours). Ethanol is a rapid-acting surface disinfectant that does NOT kill spores but is ideal for quick antisepsis and environmental surfaces. ### Mechanism and Clinical Application **High-Yield:** Ethanol denatures proteins rapidly at 70% concentration and is ideal for hand hygiene and quick surface disinfection. Glutaraldehyde is a cross-linking agent that slowly penetrates and kills all microorganisms, including spores, making it essential for reusable instruments and endoscopes. **Mnemonic:** **FAST-ETHANOL, SLOW-GLUT** — Ethanol is Fast (seconds–minutes), Glutaraldehyde is Slow (hours) but Sporicidal. ### Why Contact Time Matters 1. **Ethanol:** Immediate protein denaturation; effective within 1–2 minutes for vegetative bacteria and viruses. 2. **Glutaraldehyde:** Requires hours to penetrate spore coats and cross-link proteins; 3–10 hours for complete sporicidal activity. **Clinical Pearl:** Ethanol is used for skin prep before injections and minor procedures; glutaraldehyde is used for high-level disinfection of endoscopes and surgical instruments that cannot be autoclaved. **Warning:** Do not use ethanol for instrument disinfection if spore-forming organisms are suspected — it is NOT sporicidal. Conversely, glutaraldehyde is too toxic and slow for routine environmental disinfection.