Sterilization and Disinfection Quiz

Sterilization and Disinfection

• Sterilization is the process of killing all living microorganisms, including bacterial spores. It can be achieved by physical, chemical, or physiochemical means. Chemicals used for sterilization are called chemisterilants.
• Sterilization procedures include methods like heat, ethylene oxide gas, hydrogen peroxide gas, plasma, ozone, and radiation.
• Sterility Assurance Level (SAL) measures the probability of a microorganism surviving treatment. It's less than one in one million.
• Disinfection is the process of eliminating most pathogenic microorganisms (excluding bacterial spores) from inanimate objects. It can be achieved by physical or chemical methods. Chemicals used in disinfection are called disinfectants.
• Different disinfectants have varying effectiveness against different microorganisms. Not all disinfectants kill all microorganisms. Some methods, like filtration, separate microorganisms but do not kill them. Disinfection is not synonymous with sterilization.
• Decontamination is the process of removing contaminating pathogenic microorganisms from items. This is accomplished through sterilization or disinfection. This process uses physical or chemical means to remove, inactivate, or destroy living organisms so they are no longer infectious.
• Sanitization is a process of chemical or mechanical cleaning, used by the food industry to reduce microbes on eating utensils to safe levels for public health.
• Asepsis is the use of techniques like gloves, air filters, UV rays to achieve a microbe-free environment.
• Antisepsis is the use of chemicals (antiseptics) to make skin or mucous membranes free of pathogenic microorganisms.
• Bacteriostasis is the inhibition of bacterial growth without killing the bacteria.
• Bactericidal is a chemical that kills bacteria. Bactericidal chemicals have various names based on their target organisms, like virucidal, fungicidal, etc.
• Antibiotics are substances produced by one microbe that inhibit the growth or kill other microbes. Often the term includes synthetic and semi-synthetic antimicrobial agents.

Methods of Sterilization

• Physical Methods:
  • Sunlight: The microbicidal activity is due to ultraviolet rays that kill bacteria. It provides a natural method of disinfection for water bodies.
  • Heat: It's the most reliable sterilization method for heat-resistant articles.
• Moist heat is more effective than dry heat. Temperature and time for sterilization are inversely proportional.
• Factors affecting sterilization include the nature of heat, temperature and time, number of microorganisms, nature of microorganism, type of material, and presence of organic material.
• Different types of dry heat methods include red heat, flaming, incineration, and hot air ovens. Dry heat methods are limited to items that can take high temperatures.
• Moist heat is also used in various ways, like autoclaves or boiling. Articles that can tolerate high temperatures can be sterilized at lower temperatures by increasing the duration of exposure.
• Infrared Rays: Sterilization is achieved by high temperatures in a tunnel with infrared radiators. Articles to be sterilized are placed on conveyors. This method is well-suited for certain heat resistant articles.
• Moist Heat (Pasteurization): A common method in food and dairy industries. Techniques like the holder method (63°C for 30 minutes) and the flash method (72°C for 15 seconds) are used.

More Sterilization Methods

• Steam Sterilization (Autoclaving): Uses saturated steam under pressure to kill microorganisms and spores. Recommended for heat-sensitive instruments and other medical materials. Different types of autoclaves are also described (simple pressure cooker, steam jacketed, high pressure).
• Radiation:
  • Ionizing radiation (gamma rays, electron beams) are used to sterilize items. They are very effective and can penetrate deeply yet have disadvantages like long exposure times and special equipment requirements.
  • Non-ionizing radiation (UV rays) has limited penetration and is best suited for surface disinfection rather than sterilization.

Chemical Methods for Disinfection

• Disinfectants are chemical agents that kill pathogenic bacteria from inanimate surfaces. Some examples are:
  • Alcohols (dehydrate cells and cause protein coagulation)
  • Aldehydes (alkylate amino-, carboxyl-, or hydroxyl groups, effective on most microbes including spores)
  • Phenol & Phenolic Compounds (disrupt cell membranes and inactivate enzymes).
  • Halogens (oxidizing agents causing damage by oxidation of essential sulfur compounds in enzymes).
  • Heavy Metals (precipitate proteins and oxidize sulfydryl groups.)
  • Surface-Active Agents (concentrate at interfaces; widely used as disinfectants and antiseptics)
• Hydrogen Peroxide: An oxidizing agent that produces hydroxyl free radicals (damaging proteins and DNA). Can be used for sterilization of instruments and equipment, as well as for wound deodorization.
• Ethylene Oxide (EO) method: This is an alkylating agent typically used with a humidity-rich environment and may be used to sterilize several sensitive and heat-labile items including fabrics, plastics, rubber, and complex equipment. It's effective against spores.
• Beta-Propiolactone: An alkylating agent, often used for sterilizing biological and pharmaceutical products, is efficient and effective but can be toxic for living organisms.

Spaulding Classification

• Critical devices require sterilization to eliminate all microorganisms (e.g., surgical instruments that come into contact with sterile tissues or the bloodstream).
• Semi-critical devices require high-level disinfection (kills all vegetative microbes, inactivates most viruses and some bacterial spores) to prevent the spreading of microbes (e.g., endoscopes, respiratory devices).
• Non-critical devices require low-level disinfection (kills most vegetative microbes, some fungi, and inactivates some viruses) to reduce microbes on surfaces (e.g., furniture and tabletops).

Testing Disinfectants

• Disinfectants need to be tested to measure their effective concentration, necessary time and to monitor their activity. Several methods exist like Koch's method, Rideal Walker method, Chick Martin method, and Capacity use dilution tests. Each of them has advantages and disadvantages. Often, particular tests tend to be best for specific types of disinfectants.