Sterilization and Disinfection

Cards (61)

  • sterilization refers to the destruction of all forms of life, including bacterial spores.
  • complete removal of microorganism
    sterilization
  • Joseph lister introduced antiseptic surgery using carboxylical acid that is now call phenol
  • disinfection refers to a process that eliminates a defined scope of microorganism, including some spores
  • physical or chemical method may be used but most disinfectants are chemical agents applied to inanimate objects
  • disinfection only reduces the number of microorganism not removing them completely
  • antiseptic is a substance applied to skin for the purpose of eliminating or reducing the number of bacteria present
  • antiseptic doesn't kill spores and cannot be used as disinfectants
  • different organisms have varying ability in withstanding chemical and physical treatment due to different biochemical composition of these organisms and various mechanism that they use to protect themselves
  • is a bacteria where spores are coated with proteins, lipids, and carbohydrates as well as dipicolinic acid and calcium
    Spore forming bacteria
  • the cell wall is high in lipid which enables them to become resistant to most environmental stress such as desiccation
    myobacterium spp.
  • prions is a naked pieces of proteins, similar to viruses, but without nucleic acid, that is most resistant to the action of heat, radiation and chemicals
  • prions is an agent that able to cause the generative disease of our nervous system
  • the amount of organism present in the object yo be treated referred to as microbi load.
    Number of organisms
  • the higher the number of organism, the longer the exposure time needed to eliminate 99.9% of the microorganism
  • The amount needed to destroy microorganism varies based on the agent to be used
    concentration of disinfecting agent
  • blood, pus, and mucus are examples of organic materials that may prevent full contact of agent to the organic, hence limiting its action
    presence of organic material
  • instrument that we use in lab sometimes are made up of biomaterial which exempts them to disinfection or sterilization due to possible damage
    nature of surface to be disinfected
  • It is critical to observe proper contact time of the agent and the object to be disinfected or sterilized
    • too little contact time does not allow the agent to work properly
    contact time
  • disinfectants are usually used at room temperature (20 to 22°C.)
    • too high to low temp may inactive disinfectants and sterilants

    Temperature
  • It is important important consider the pH of the material to be treated and the agent itself.
    • Manufacturers usually optimize this factor to achieve maximum activity
    pH
  • certain bacteria have the ability to form communities of layers of bacteria with protective shield called

    biofilm
  • biofilm formation may require longer contact time or increase in the concentration of the agent
  • some disinfectants may inactivate the action of each other hence it is important to consider the
    compatibility of disinfectants
  • autoclave operates based on the principle of steam under pressure.
    • Sterilization: 121 degrees celsius from 15lbs/ in2 for 15mins
    • Decontamination: 135 degrees celcius for 30lbs/in2 for 30mins
  • Biological indicator of autoclave is geobacillus stearothermophilus
    • purple indicates nonsterility
    • yellow indicates sterility
  • Tyndalization is a fractional discontinuous sterilization and discontinuous heating
    • Effective indication: 100 degree celsius for 30-60minutes
    • Instrument: Arnold's sterilizer
  • Inspissation is thickening through evaporation
    • Effective indication: 75-80 degrees celsius for 2 hours
    • Instrument: Inspissator
  • Direct heat: direct application of flame in aseptic technique; until red hot
  • Dry/Hot air oven: sterilization of heat resistant materials
    • EI: 160-180° C for 1.5 to 2 hours
  • Biological Indicator of Dry/Hot Oven: Bacillus atropheus
  • Incineration: burns materials into ashes; used in the disposable of biological wastes
    • EI: 870-980° C for 2 seconds
  • Ionizing Radiation works by alkylation of nucleic acid of bacteria using high energy short wavelength deep penetrating gamma rays
    • used for heat sensitive materials
  • biological indicator of ionizing radiation: Bacillus Pumilis
  • Filtration used membrane filters that are usually made of plastic polymers or cellulose esters that contains pores
  • Filtration
    Water/ liquid solutions/ antibiotics/ vaccines
    • usually uses a thin membrane filter of cellulose acetate with different pore size depending on the intended purpose
  • Filtration
    Water/ liquid solution/ antibiotics/ vaccines:
    • 0.45-0.80 Mm - most bacteria, yeast, and molds are retained but may allow passage of Pseudomonas like organisms.
  • Filtration Water/ liquid solution/ antibiotics/ vaccines
    • 0.22 Mm - used to filter Pseudomonslike organisms; used for critical sterilization of parental solutions
  • Filtration
    Water/ liquid solution/ antibiotics/ vaccines:
    • 0.01 Mm - able to retain small viruses
  • Filtration
    Air: High Efficiency Particulate Filte (HEPA)
    • has a pore size of 0.03Mm; usually used in biological safety cabinet and rooms of immunocompromised patients