Sterilization Methods

Study Notes

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

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

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

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

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

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.

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.

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.

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.

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 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 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 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).