Sterilization and Antiseptics Overview

Sterilization, Disinfectants, and Antiseptics

• Sterilization: Killing all forms of microbes, including spores.
• Disinfectants: Antimicrobial agents applied to non-living objects to reduce pathogenic microorganisms.
• Antiseptics: Antimicrobial substances applied to living tissue to reduce infection risk, without damaging the tissue. Not all disinfectants are antiseptics; antiseptics must be less harsh.

Sterilization Methods

• Divided into chemical and physical methods.
• Chemical Sterilization: Typically used for devices sensitive to high heat or irradiation (e.g., rubbers, plastics).
  • Further divided into chemical liquid sterilization and chemical vapor sterilization.
• Physical Sterilization: Uses physical agents to eliminate microorganisms from surfaces, equipment, and materials.
  • Includes autoclaving (moist heat), dry heat sterilization, filtration, radiation, and ultraviolet (UV) radiation.

Chemical Liquid Sterilization

• High-level disinfectants: Effective for a large number of spores and microbes after prolonged exposure. Examples include hydrogen peroxide (3-6%), and 70% ethyl alcohol and isopropyl alcohol.
• Intermediate-level disinfectants: Effective against some spores but lower than high-level. Examples include enveloped viruses (HBV, HIV)
• Low-level disinfectants: Primarily effective against vegetative bacteria, fungi, and some viruses. Examples include Iodine 5 and 10%, and Providone-iodine.

Chemical Vapor Sterilization

• Chemical Vapor under pressure (Chemiclave): Uses a mixture of chemicals (alcohol, formaldehyde, ketone, acetone, water) heated under pressure to form a sterilizing gas. Requires 20 minutes at 131°C and 20 lbs pressure.
• Fumigation: Potassium permanganate mixed with formalin, in a specific ratio (2:3 w/v) for effective sterilization.

Physical Sterilization Methods

• Autoclaving (Moist Heat Sterilization): Uses pressurized steam at 121°C (250°F) for 15-20 minutes effective for sterilizing media, lab instruments, and biohazardous waste.
• Dry Heat Sterilization: Uses high temperatures (160-180°C) for a long duration in a dry heat oven, suitable for sterilizing metal instruments, glassware, and powders.
• Filtration: Removes microorganisms by passing liquids or air through filters with small pores (e.g., 0.2 microns). Useful for heat-sensitive liquids.
• Radiation (Ionizing Radiation): Using gamma rays or electron beams to break down DNA in microorganisms. Useful for sterilizing medical equipment, plastics, and pharmaceuticals
• Ultraviolet (UV) Radiation: Uses UV-C light (254 nm) to damage the DNA of microorganisms, preventing replication. Used for surface sterilization.

Additional Sterilization Methods

• Boiling: Water at 100°C (212°F) for 10-15 minutes kills some bacteria and viruses, but not spores.
• Incineration: Destroying contaminated materials by burning at high temperatures.

Diagnostics of Bacteria

• Microscopy: Techniques like Gram staining (Gram-positive vs. Gram-negative) and Acid-Fast staining (identifying Mycobacterium species) for classifying bacteria based on cell wall structure.
• Culture Methods: Using various media (Agar Plates, Broth Cultures) to promote bacterial growth and identification by observing colony morphology.
• Biochemical Testing: Methods like Catalase, Coagulase, Oxidase, and Urease tests to identify specific bacterial types based on enzyme presence.
• Automated Systems: Automated biochemical tests (VITEK and BD Phoenix) for faster bacterial identification.
• Molecular Methods: Using Polymerase Chain Reaction (PCR) to detect bacterial DNA.

Blood Analysis

• Complete Blood Count (CBC): Automated machines (hematology analyzers) count blood cells, measure hemoglobin, and perform other parameters.
• Blood Smear Microscopy: Visualizes blood cells under a microscope to diagnose conditions like leukemia and anemia.
• Hemoglobin and Hematocrit Tests: Measures hemoglobin concentration and proportion of red blood cells (RBCs) to detect anemia.
• Blood Coagulation Tests: Tests like Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) to assess blood clotting function.

Laboratory Safety

• First Aid: Keep first aid kits, eyewash stations, and showers readily available.
• Biochemical Hazards: Use proper storage and disposal of chemicals in accordance with safety measures.
• Biological Hazards: follow appropriate safety protocols, use biological safety cabinets and disinfect surfaces.
• General Safety: Adhere to Standard Operating Procedures (SOPs) and maintain safety equipment.