Microorganisms and Sterilization Techniques

Introduction

• Microorganisms are everywhere and can cause issues like food spoilage and disease.
• Killing or inhibiting their growth is essential.
• This aims to destroy pathogens and prevent transmission.
• It also reduces or eliminates microorganisms contaminating water, food, and substances.

Definitions

• Sterilization: A process that removes all living microorganisms, including those in vegetative or spore states.
• Sterile: Any material that has been sterilized.
• Germicide: A chemical agent killing pathogenic microorganisms.
• Disinfection: Destroys or removes all pathogenic organisms capable of causing infection. It kills vegetative pathogens but not bacterial endospores.
• Sepsis: The growth of microorganisms in the body or the presence of microbial toxins in blood and other tissues.

Filtration

• An excellent way to reduce the microbial population in heat-sensitive solutions using different types of filters.
• Filters physically remove contaminants rather than destroying them.
• Depth Filters: Made of fibrous or granular materials bonded into a thick layer with twisting channels.
  • Candle Filters: Diatomaceous earth (Berkefeld) or unglazed porcelain (Chamberlain). Used for water purification.
  • Asbestos Filters: Made from asbestos like magnesium silicate. Seitz and Sterimat are disposable discs.
  • Sintered Glass Filters: Made from fused finely powdered glass particles. They are brittle and expensive.
• Membrane Filters: Composed of cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene fluoride, or other synthetic materials. They are circular porous membranes.

Asepsis

• Refers to any practice that prevents the entry of infectious agents into sterile tissues, preventing infection.
• Antiseptics: Chemicals applied to exposed body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens.
• Sanitization: A cleansing technique mechanically removing microorganisms and food debris to reduce contaminants.
• Sanitizers: Compounds like soap or detergents used for sanitization.
• Degerming: Reducing the number of microbes on the human skin. Done by scrubbing or immersing in chemicals.

Sterilization Methods

• Physical Methods:
  • Sunlight
  • Heat
  • Filtration
  • Radiation
  • Sound waves
• Chemical Methods:
  • Specific chemicals used to kill bacteria or limit their growth

Sunlight

• A natural method of sterilization for water in tanks, rivers, and lakes.
• Direct sunlight has an active germicidal effect that destroys microorganisms in water sources.