Microbiology: Sterilization Methods Quiz

Sterilization, Disinfection, and Antisepsis

• Students should be able to define sterilization, disinfection, and antisepsis.
• Methods of sterilization and disinfection include physical, chemical, and mechanical removal methods.
• Microorganisms cause contamination, infection, and decay.
• Early civilizations used methods like salting, smoking, pickling, and sunlight exposure to preserve food.
• Aseptic techniques were developed in the mid-1800s to prevent contamination of surgical wounds.
• Nosocomial infections (hospital-acquired infections) were a major problem before the development of these techniques, with 10% of surgical patients and up to 25% of mothers in hospitals dying from infections.
• Microbial growth control methods include altering membrane permeability, damaging proteins, and damaging nucleic acids.
• Prions are the most resistant, followed by bacterial spores, mycobacteria, cysts/protozoa, vegetative cells, (Gram-negative/positive) bacteria, fungi, viruses without envelopes, and viruses with lipid envelopes.
• Sterilization is the process of removing all microorganisms, including spores.
• Autoclaving, a common sterilization method, involves exposing materials to steam at 121°C under 15 lb/in² pressure for 15 minutes.
• Surgical instruments are sometimes sterilized by ethylene oxide gas, or intravenous solutions by filtration.

Methods of Sterilization

• Methods of sterilization include physical, chemical, and mechanical agents.

Physical Agents:

• Heat (dry and moist), radiation (non-ionizing and ionizing).
  • Dry heat methods use ovens to kill microbes.
  • Moist heat methods such as autoclaving use steam under pressure. Autoclaving occurs at 121 to 132 degrees celsius at various times.
  • Radiation methods to sterilize include ionizing radiation using X-rays, gamma rays, and cosmic rays and non-ionizing radiation using ultraviolet.

Chemical Agents:

• Gases (ethylene oxide, hydrogen peroxide vapor, plasma gas)
• Liquids (peracetic acid, glutaraldehyde)
• Sterilization by chemical agents also uses disinfectants in liquids that include, formaldehyde, glutaraldehyde, chlorine, and phenols, and in solution in alcohol.
• Disinfectants kill most, but not all microbes, while antiseptics are used on living tissue.

Mechanical Removal:

• Filtration (air and liquids)

Disinfection

• Disinfection kills many microorganisms, but not all, including bacterial spores.
• Disinfectants are used on inanimate objects and materials.
• Antiseptics kill microbes on living tissue.
• Disinfection methods include moist heat (boiling water, pasteurization), liquids (alcohol, chlorine, phenols, hydrogen peroxide). Different chemicals have different effects and effectiveness.

Definition of Sterilization

• Sterilization is the process of freeing an object from all microorganisms, including spores.

Learning Outcomes

• define sterilization, disinfection, and antisepsis.
• understand methods of sterilization and disinfection
• explain the role of sterilization and disinfection in disease control.

Terminology

• degermation
• sepsis
• asepsis
• bactericidal
• bacteriostatic
• antiseptic
• sterilization
• disinfection
• sanitation
• sporicidal

Antiseptic Agents

• various disinfectants and antiseptics work differenly and are used in differing concentrations based on intended goal.

Methods of Disinfection

• Different methods (Moist Heat, Liquid) have differing concentration/temperature levels.

Uses of Sterlization and Disinfection Processes

• various chemicals are used for different purposes, ranging from preserving specimens to sterilizing equipment for surgery.

Principles of effective disinfection

• Concentration of disinfectant
• Organic matter
• pH
• Time

Alcohols

• Ethanol/Isopropyl alcohol
• effective against enveloped viruses at a high concentration
• No action on spores

Aldehydes

• Formaldehyde
• Glutaraldehyde
• highly effective disinfectants

Halogens

• Iodine
• Chlorine-based compounds
• useful for disinfection in water and swimming pools

Phenols

• Phenol-based compounds
• highly effective in hospitals.

Hydrogen Peroxide

• Used as an antiseptic for cleaning wounds.

Gases for Sterilization

• Ethylene oxide
• Used for sterilization of heat-sensitive materials like heart-lung machines, respirators, sutures, and clothing, as well as some plastics, glass, metals, and some foods/tobacco.

Metallic Salts

• Salts of silver, copper, and mercury are disinfectants. They coagulate proteins, inhibit bacterial growth.

Sterilization By Filtration

• Removes bacteria from heat-sensitive liquids like sera and antibiotics using filters like asbestos, candle, membrane, and sintered glass filters.

Radiation methods for sterilization

• Ionizing radiation includes X-rays, gamma rays, and cosmic rays, and are used to sterilize plastic syringes and catheters, fabrics, metals and grease foils..
• Non-ionizing radiation includes UV light, and is used for rapid mass sterilization of pre-packaged syringes and catheters.

Ultrasonic and Sonic Vibration

• Microorganisms vary in their sensitivity.
• Not effective in sterilization or disinfection.