Micropara week 5

• Microbial population growth is exponential and influenced by environmental factors
• Solid objects can be sterilized by physical agents like heat and radiation, while liquids and gases are sterilized by heat, radiation, and filtration
• Chemical agents do not readily destroy bacterial endospores and are used as disinfectants, sanitizers, and antiseptics
• Objects can be sterilized by gases like ethylene oxide that destroy endospores
• Sterilization is the process by which all living cells, viable spores, viruses, and viroids are destroyed or removed from an object or habitat
• A sterile object is totally free of viable microorganisms, spores, and other infectious agents
• Disinfection is the killing, inhibition, or removal of microorganisms that may cause disease
• Disinfectants are agents used to carry out disinfection and are usually used on inanimate objects
• A germicide kills pathogens but not necessarily endospores
• Conditions influencing the effectiveness of antimicrobial agent activity include population size, composition, concentration, duration of exposure, temperature, and local environment
• Heating, desiccation, freezing, filtration, radiation, sonic and ultrasonic vibrations, and osmotic pressure are physical methods used for microbial control
• Moist heat sterilization methods include pasteurization, vaccine bath, serum bath, and inspissation
• INSPISSATION:

  • Used to solidify and disinfect egg-containing and serum-containing bacteria
  • Heated at 80-85 degrees Celsius for 30 minutes for three successive days
  • Process: on the first day, vegetative forms die, and spores germinate into vegetative forms which are then killed on subsequent heating
• HEATING: MOIST HEAT:

  • Boiling involves utilizing water at 100 degrees Celsius, destroying only vegetative forms
  • Fractional Sterilization (Tyndallization) involves live steam at 100 degrees Celsius for 30-90 minutes for three consecutive days, killing vegetative forms on the first day and spores on the second day
• HEATING: DRY HEAT:

  • Methods include Red Flame, Open Flame, Incineration, Hot air oven, and Infrared Rays
  • Red Flame sterilizes articles like bacteriological wire loops by heating them until red hot
  • Open Flame aims to burn organisms into ashes, used for sterilizing test tubes, scalpels, and glass slides
  • Incineration burns contaminated material like soiled dressings and animal carcasses
  • Hot air oven, introduced by Louis Pasteur, sterilizes articles at 160 degrees Celsius for one hour, used for glassware and powders
• FILTRATION:

  • Removes contaminating microorganisms without destroying them
  • Used for sterile heat-sensitive materials like vaccines, enzymes, and antibiotics
  • Examples include HEPA Filters for air and Membrane Filters for liquids
• RADIATION:

  • Ultraviolet Light (UVL) induces formation of thymine-thymine dimers, inactivating microorganisms within seconds
  • Ionizing Radiation causes free radicals to interact with proteins and nucleic acids, resulting in cell death
  • Types include Electron Beams and Electromagnetic Rays (Gamma Rays)
• SONIC AND ULTRASONIC VIBRATIONS:

  • Some
• High energy sources like gamma rays and X-rays are more penetrating than electron beams but require longer exposure time
• High energy sources cause damage to microorganism’s nucleic acid
• High energy sources like gamma rays and X-rays are bactericidal, fungicidal, virucidal, and sporicidal
• High energy sources are used to sterilize commercially disposable petri dishes, plastic syringes, vitamins, antibiotics, hormones, fabrics, and glassware
• Sonic and ultrasonic vibrations can kill some bacteria and viruses after exposure to certain frequencies of sound waves
• High frequency sound waves act by disrupting cells, disinfecting and cleaning instruments, and reducing microbial load
• Osmotic pressure is based on the principle of Osmosis, creating a hypertonic environment (high concentration of salts and sugar) that causes bacterial cells to collapse
• Osmotic pressure is used for the preservation of fruits in syrup and meats
• Factors affecting the efficacy of chemical agents include concentration and potency, duration of exposure, temperature, nature of the surrounding medium, nature of the organisms, and number of organisms/size of inoculum
• Characteristics of a good chemical agent include being broad spectrum, fast-acting, active in the presence of organic matter, active in any pH, stable, non-toxic, non-allergic, non-irritative, non-corrosive, soluble in water, easy to apply, leaving a residual antimicrobial film on the treated surface, having high penetrating power, being readily available, safe under storage and shipping for reasonable periods of time, and not having a bad odor
• Classification of chemical disinfectants is based on consistency (liquid or gaseous), spectrum activity (High level, Intermediate level, Low level), and mechanism of action (damage to the cell membrane, denaturation of cellular proteins, modification of the functional groups of proteins and nucleic acids)
• Surface active agents, like surfactants, disrupt membranes resulting in leakage of cell membranes, are active against vegetative microbial forms including mycobacteria and enveloped viruses, and are widely used in homes and hospitals
• Phenolic compounds disrupt cell membranes, cause precipitation of proteins, and inactivate enzymes, being bactericidal and fungicidal, good against Mycobacteria but poor activity against spores and most viruses
• Alcohols disorganize the lipid structure of the cell membrane, dehydrate the cells, and cause denaturation and coagulation of cellular proteins, with 70% aqueous solution being better, but they can be skin irritants and flammable
• Alcohols include ethyl alcohol used as a skin antiseptic, isopropyl alcohol greater bactericidal than ethyl alcohol, benzyl alcohol mainly for preservation, and methyl alcohol fungicidal and sporicidal
• Heavy metals cause damage to the enzyme of bacteria, precipitation of proteins, and oxidation of sulfhydryl groups, being mostly bacteriostatic than bactericidal
• Halogens are bactericidal oxidizing agents that cause oxidation of essential sulfhydryl groups of enzymes, leading to enzyme inactivation, with iodine being the best antiseptic and chlorine used for water treatment and disinfection
• Aldehydes like formaldehyde and glutaraldehyde damage nucleic acids by alkylation of amino-, carboxyl-, or hydroxyl groups, killing all microorganisms including spores
• Formaldehyde is used for surface disinfection and sterilization of bedding and furniture, while glutaraldehyde is sporicidal and used as a cold sterilant in medical equipment
• Ethylene oxide is sporicidal and used in gaseous sterilization processes for heat-sensitive materials or equipment, being highly flammable and causing eye irritation
• Ethylene oxide is more potent than glutaraldehyde but slower-acting, requiring a combination with 10% CO2 and causing eye irritation, being mutagenic and carcinogenic