Sterilization and Disinfection

• Joseph Lister (1827-1912) was a British surgeon who introduced the concept of "aseptic surgery" and promoted sterile surgery by using carbolic acid (phenol) to sterilize surgical instruments and clean wounds
• Lister's work significantly reduced the risk of infection in surgery and saved countless lives
• Sterilization is the destruction of all life forms, including spores, in an all-or-nothing process
• Disinfection is the elimination of a defined scope of microorganisms, including some spores, and can involve elimination, inhibition, or removal of pathogens
• Disinfection processes may not cause sterilization and are influenced by factors like types of organisms, number of organisms, concentration of disinfecting agent, presence of organic material, nature of the surface, contact time, temperature, pH, and biofilms
• Biofilms are communities of microorganisms living in a self-produced matrix of extracellular polymeric substances (EPS) that can cause infections, corrosion, and other damage, and are resistant to antibiotics and other antimicrobial agents
• The formation of a biofilm begins with bacteria attaching to a surface, producing EPS to hold the biofilm together and protect it, allowing it to grow and expand as new bacteria join the community
• Prions are the most resistant organisms, followed by bacterial spores, mycobacteria, nonlipid viruses, fungi, bacteria, and lipid viruses
• Different types of organisms vary in their ability to withstand chemical and physical treatment due to their biochemical compositions and protective mechanisms
• High-level disinfectants are active against bacterial endospores, intermediate-level disinfectants have tuberculocidal activity but not sporicidal, and low-level disinfectants are active against microorganisms but not sporicidal or tuberculocidal
• Physical methods of sterilization and disinfection include heat, filtration, radiation, alcohols, aldehydes, halogens, chlorine compounds, detergents, phenolics, heavy metals, and gases
• Joseph Lister, a British surgeon, is considered the father of modern antiseptic surgery for introducing carbolic acid to reduce infection risk

  
• Joseph Lister, a British surgeon and scientist, developed antiseptic surgery in the 1860s, saving countless lives and revolutionizing the field

  
• A biofilm is a community of microorganisms living in a self-produced matrix of extracellular polymeric substances (EPS) on surfaces like metal, plastic, glass, and living tissue
• Biofilm formation starts with bacteria attaching to a surface, producing EPS to hold the biofilm together and protect it, allowing it to grow and expand as new bacteria join
• Biofilms can cause infections, corrosion, and other damage, being resistant to antibiotics and other antimicrobial agents
• Physical methods like heat under steam pressure in an autoclave at 121°C for 15 min kill all microorganisms and endospores, except prions
• Dry heat requires higher temperatures and longer exposure times, e.g., 1.5 to 3 hours at 160-180°C, commonly used to sterilize glassware
• Boiling for 15 minutes at 100°C kills most microorganisms, while pasteurization at 63°C for 30 minutes or 72°C for 15 seconds is used in the food industry
• Filtration methods use thin membrane filters with specific pore sizes to retain bacteria, yeasts, and molds, with critical materials requiring a 0.22-µm filter
• Filtration is commonly used for sterilizing heat-sensitive solutions like parenteral solutions, vaccines, and antibiotic solutions
• Chemical methods, like phenolics, act by reacting with components of the cytoplasmic membrane, denaturing cellular proteins, and damaging RNA and DNA to inhibit microorganism replication
• Phenolics, including chlorhexidine gluconate and chloroxylenol, are used as topical antiseptics and for hand hygiene in healthcare settings
• Alcohols like ethyl and isopropyl alcohol are effective against enveloped viruses, bacteria, fungi, and M. tuberculosis, but not non-enveloped viruses or spores
• Halogens like iodine and chlorine are highly oxidizing agents used for disinfection, with povidone-iodine being a common skin antiseptic
• Aldehydes like formaldehyde and glutaraldehyde are used for sterilization, with glutaraldehyde being the choice for medical equipment that is not heat-stable
• Heavy metals like silver nitrate and mercuric chloride are rarely used due to high toxicity and slow activity, while gases like ethylene oxide are commonly used for sterilization
• Detergents and quaternary ammonium compounds disrupt cellular membranes, making them sporicidal or tuberculocidal for disinfecting noncritical surfaces
• Prions, resistant to formaldehyde, radiation, and detergents, can be eliminated with an autoclave for 1 hour, 5% hypochloride solution, or 1.0 M sodium hydroxide
• Joseph Lister, a British surgeon, introduced the concept of "aseptic surgery" and successfully used carbolic acid (phenol) to sterilize surgical instruments and clean wounds

  
• Lister was a pioneer in controlling infections in laboratories and healthcare facilities, focusing on nosocomial infections
• Sterilization is the destruction of all life forms, including spores, while disinfection eliminates a defined scope of microorganisms, including some spores
• Disinfection processes may not cause sterilization and can be applied to inanimate objects as disinfectants or to the skin as antiseptics
• Antisepsis involves the prevention of infection or sepsis using antiseptics, which are chemicals directly applied to body surfaces, wounds, or body parts to kill or inhibit the growth of vegetative pathogens
• Factors influencing the "killing" ability of disinfectants include the types and number of organisms, concentration of the disinfecting agent, presence of organic material, nature of the surface, contact time, temperature, pH, and biofilms
• Different types of organisms vary in their ability to withstand chemical and physical treatment due to their biochemical compositions and protective mechanisms
• Prions are the most resistant organisms, followed by bacterial spores, mycobacteria, nonlipid viruses, fungi, bacteria, and lipid viruses
• The microbial load or bioburden determines the exposure time needed for the elimination of microorganisms, with higher numbers requiring longer exposure times
• Presence of organic material like blood, mucus, or pus can inactivate disinfecting agents, emphasizing the need to cleanse surfaces before disinfection
• Biofilms, communities of microorganisms with a protective matrix, make disinfection challenging and may require increased concentration and contact time of disinfectants