Overview
This lecture covers alcohols as chemical control agents, focusing on their types, mechanisms, effectiveness, concentrations, and use as disinfectants and antiseptics.
Types of Alcohols Used for Chemical Control
- Two main types: Ethanol (drinking alcohol) and Isopropanol (rubbing alcohol).
- Both are used to control microbial growth.
Mechanism of Action
- Alcohols denature (unravel) proteins, causing them to lose function.
- Alcohols disrupt lipid membranes of microbes.
Applications: Disinfectants vs. Antiseptics
- Disinfectants are for surfaces; antiseptics are for living tissue.
- The same alcohol can serve as either, depending on use.
Effectiveness and Limitations
- Alcohols can kill many bacteria, some fungi, and envelope viruses.
- They are not effective against non-envelope (naked) viruses.
- Alcohol is volatile—evaporates quickly, so its effect is immediate and short-lived.
- Most effective when used right after application (e.g., swabbing skin before injection).
Optimal Concentration and Comparative Efficacy
- Both alcohols work best at 70% concentration for killing microbes.
- Water is necessary for membrane disruption and protein denaturation; 100% alcohol is less effective.
- Isopropanol (rubbing alcohol) is slightly more effective than ethanol.
Key Terms & Definitions
- Alcohols — Chemicals like ethanol and isopropanol used to control microbes.
- Denature — Process where proteins lose their shape and function.
- Disinfectant — Chemical used on non-living surfaces to kill microbes.
- Antiseptic — Chemical used on living tissue to kill microbes.
- Envelope Virus — Virus surrounded by a lipid membrane, susceptible to alcohol.
- Volatile — Easily evaporates at room temperature.
Action Items / Next Steps
- Remember: 70% alcohol is currently the most effective concentration for microbial control.
- Know that isopropanol is slightly more effective than ethanol for disinfection purposes.