Sterilization and Disinfection

1. Sterilization and Disinfection -By Dr. Preeti Tyagi (MBBS,MD) Professor of Physiology VMMC & Sufdarjung Hospital New Delhi

2. Introduction • Sterilization and disinfection are essential practices in microbiology and clinical settings. They help prevent infections, ensure safety in surgeries, and maintain lab hygiene. • Key Definitions: • Sterilization: Destruction or removal of all forms of microbial life, including spores. • Disinfection: Elimination of most pathogenic microbes (excluding spores) from inanimate objects.

3. Levels of Disinfection • High-level – Destroys all microorganisms except high numbers of bacterial spores (e.g., glutaraldehyde) • Intermediate-level – Kills mycobacteria, most viruses, and fungi (e.g., alcohols, phenolics) • Low-level – Eliminates most bacteria and some viruses (e.g., quaternary ammonium compounds)

4. Physical Methods • Chemical Methods Methods of Sterilization • Moist heat • Dry heat • radiation • Filtration • Ethylene oxide • Formaldehyde • Hydrogen peroxide

5. Methods of Sterilization Physical/Chemical • Moist Heat Sterilization • Uses steam under pressure (Autoclave) • 121°C for 15–20 minutes • Kills spores • Commonly used for surgical instruments, media • Dry Heat Sterilization • Hot air oven (160°C for 2 hours) • Used for glassware, powders • Filtration • For heat-sensitive liquids (e.g., antibiotics, serum) • Radiation • UV light – surface disinfection • Ionizing radiation – sterilizes disposable equipment • Ethylene Oxide Gas – for heat-sensitive instruments • Glutaraldehyde – high-level disinfectant, used for endoscopes • Formaldehyde – used for fumigation • Hydrogen Peroxide Vapor – surface and room sterilization

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7. Common Disinfectants in Hospitals • Alcohols (70% ethanol/isopropanol) – skin and surface disinfectant • Chlorine compounds (bleach) – effective against viruses and bacteria • Phenolics – used for environmental surfaces • Quaternary ammonium compounds – floors, furniture • Iodophors – pre-operative skin preparation

8. Factors Affecting Efficacy • 🦠 Type and Number of Microorganisms: Some microbes (e.g., bacterial spores, mycobacteria) are more resistant. A higher microbial load requires stronger or prolonged treatment. • 🩸 Presence of Organic Matter: Blood, pus, or mucus can interfere with disinfectant action. Organic material protects microbes and inactivates some agents. • 🧪 Concentration and Contact Time: Stronger solutions are generally more effective, but must be used safely. Adequate contact time ensures complete microbial kill. • 🌡️ pH and Temperature: Some disinfectants work better at specific pH levels or temperatures. For example, chlorine is more effective in acidic pH. • 🧱 Nature of Surface or Material: Porous or rough surfaces may hide microbes. The material (metal, plastic, rubber) also affects the choice of sterilizing method.

9. Quick Summary • Sterilization kills all microorganisms; disinfection kills most • Both are essential to infection control • Choose the method based on material type and risk • Understand agent effectiveness and safety 📲 Tip for Students: Revise microbiology faster with TurningBrain App – includes full video lectures, MCQs, and notes for sterilization, disinfection, and more.

10. THANK-YOU • Full Physiology Course is available on Turning Brain App • by The Best Physiology Faculty in india, Dr. Preeti Tyagi • For More Info. +91-8368648746 www.turningbrain.in https://youtube.com/@dr.preetityagilectures874?si=YfbJEi66jOE0hjzu APP LINKS Android: https://play.google.com/store/apps/details id=tbrain.in.medical.eduapp&hl=en_IN IOS: https://apps.apple.com/in/app/turning-brain-dr-preeti-tyagi/id6502828714