Sterilization Methods

Sterilization Methods

Sterilization is a process that completely eliminates all forms of microbial life, including spores. The following are common sterilization methods:

Heat Sterilization

• Moist Heat Sterilization (Autoclaving)
  • Uses high-pressure steam to kill microorganisms
  • Temperature: 121°C (250°F) for 15-30 minutes
  • Effective against all microorganisms, including spores
• Dry Heat Sterilization
  • Uses hot air to kill microorganisms
  • Temperature: 160°C (320°F) for 2 hours
  • Effective against all microorganisms, including spores

Radiation Sterilization

• Ionizing Radiation
  • Uses gamma rays or electron beams to kill microorganisms
  • Effective against all microorganisms, including spores
  • Commonly used for sterilizing medical instruments and pharmaceuticals
• Ultraviolet (UV) Light
  • Uses UV light to kill microorganisms
  • Effective against bacteria and viruses, but not spores
  • Commonly used for surface disinfection

Filtration Sterilization

• Membrane Filtration
  • Uses filters with small pores to remove microorganisms
  • Effective against bacteria and viruses, but not spores
  • Commonly used for sterilizing liquids and gases

Chemical Sterilization

• Ethylene Oxide (ETO) Sterilization
  • Uses ETO gas to kill microorganisms
  • Effective against all microorganisms, including spores
  • Commonly used for sterilizing heat-sensitive materials
• Hydrogen Peroxide Gas Plasma Sterilization
  • Uses hydrogen peroxide vapor to kill microorganisms
  • Effective against all microorganisms, including spores
  • Commonly used for sterilizing medical instruments and equipment

Sterilization Methods

• Sterilization is a process that completely eliminates all forms of microbial life, including spores.

Heat Sterilization

• Moist Heat Sterilization (Autoclaving) uses high-pressure steam to kill microorganisms at a temperature of 121°C (250°F) for 15-30 minutes, effective against all microorganisms, including spores.
• Dry Heat Sterilization uses hot air to kill microorganisms at a temperature of 160°C (320°F) for 2 hours, effective against all microorganisms, including spores.

Radiation Sterilization

• Ionizing Radiation uses gamma rays or electron beams to kill microorganisms, effective against all microorganisms, including spores, commonly used for sterilizing medical instruments and pharmaceuticals.
• Ultraviolet (UV) Light uses UV light to kill microorganisms, effective against bacteria and viruses, but not spores, commonly used for surface disinfection.

Filtration Sterilization

• Membrane Filtration uses filters with small pores to remove microorganisms, effective against bacteria and viruses, but not spores, commonly used for sterilizing liquids and gases.

Chemical Sterilization

• Ethylene Oxide (ETO) Sterilization uses ETO gas to kill microorganisms, effective against all microorganisms, including spores, commonly used for sterilizing heat-sensitive materials.
• Hydrogen Peroxide Gas Plasma Sterilization uses hydrogen peroxide vapor to kill microorganisms, effective against all microorganisms, including spores, commonly used for sterilizing medical instruments and equipment.

Cell Wall Structure

• Bacterial cell walls are composed of peptidoglycan (murein), a unique polymer that provides shape and maintains cellular integrity.
• Cell walls can be divided into two main categories:
  • Gram-positive: thick peptidoglycan layer, teichoic acids present, and no outer membrane.
  • Gram-negative: thin peptidoglycan layer, lipopolysaccharides present, and outer membrane.

Flagella And Motility

• Flagella are whip-like structures composed of protein filaments that enable bacterial movement.
• Types of flagella:
  • Monotrichous: single flagellum at one pole.
  • Lophotrichous: multiple flagella at one pole.
  • Peritrichous: multiple flagella scattered over the entire cell surface.
• Motility allows bacteria to:
  • Find nutrients and optimal environments.
  • Escape from predators and toxic substances.
  • Infect and colonize host tissues.

Capsules And Biofilms

• Capsules are outer layers of polysaccharides or polypeptides that provide protection and aid in adhesion.
• Biofilms are complex communities of bacteria adhered to surfaces, embedded in a matrix of extracellular polymeric substances (EPS).
• Functions of capsules and biofilms:
  • Protection from phagocytosis and antimicrobial agents.
  • Enhanced adhesion and colonization.
  • Improved resistance to environmental stresses.

Bacterial Disease

• Bacterial diseases can be caused by:
  • Toxins: proteins or other molecules produced by bacteria that harm host cells.
  • Invasion: direct invasion of host tissues by bacteria.
  • Immune system evasion: bacteria can evade or manipulate the host immune system.
• Examples of bacterial diseases:
  • Tuberculosis (Mycobacterium tuberculosis).
  • Pneumonia (Streptococcus pneumoniae).
  • Food poisoning (Salmonella and Escherichia coli).
  • Anthrax (Bacillus anthracis).