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Physical Agents
i.e. Heat or Radiotion
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Chemical Agents
i.e. disinfectants and antiseptics
-
Highest resistance to microbial control
- Prions
- Bacterial endospores
-
Moderate resistance to microbial control
- Protozoan Cysts
- Naked Viruses
- Hep B
- Polovirus
-
Least resistant to microbial control
- Fungal spores
- eveloped viruses
- yeasts
- protozoan trophozoites
- bacterial vegetative spores
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Bacterial Spores
- considered most resistant
- 18x's harder to destroy than vegetative cells
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Sterilization
- Destroys or removes ALL viable microorganisms including viruses
- For inanimate objects
- usually accomplished through heat but also through some chemicals called sterilants
-
Microbicidal
- Kills microbes
- Can be highly toxic to human cells
-
Microbistasis
- temporarily prevents cells from multiplying
- not killed outright.
-
Disinfection
- Physical or chemical agent to destroy vegetative pathogens
- NOT bacterial
- For inanimate objects
-
Sepsis
Growith of microorganisms in blood and other tissues
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Asepsis
PREVENTS entry of infectious agents into sterile tissues to prevent infection
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Microbial Load
Microbial population
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Santization > Sterilization
-
Degermation
- Reduction of microbial load through mechanical means on living tissue
- i.e. surgical hand soap and alcoholic wipes
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Microbicidal Agent
With time and concentration targets the metabolic process in a cell
-
Active cells die more quickly than older
More metabolic activity to target versus less
-
Effectiveness of agent governed by:
- 1) # of Microorganisms- more means longer
- 2) Nature of microorganisms in population- more variation means more resistance
- 3) Temperature of pH in environment
- 4) Concentration (dosage, intensity) of agent
- 5) Mode of action- Kill or Inhibit
- 6) Presens of solvents or interfering organic matter (i.e. blood, saliva, feces)
-
Cellular targets of physical and chemical agents
- 1) Cell Wall (blocks synthesis & surface is broken down)
- 2) Cell membrane (2 way communication is disrupted- bad is let in and good not protected)
- 3) Cellular synthetic processes (DNA & RNA)- (Vital protens inhibited)
- 4) Proteins (Breaks down native state bonds)
-
Temperature that exceeds maximum growth temperature is
Microbicidal
-
Tempuratures lower than minimum growth temperature are
microbistatic
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Moist Heat
- hot or boiling water
- steam
- 60 to 135 C
- Lower temps and shorter exposure
-
Dry Heat
- Air with low moisture content heated by flame or electirc heating coil
- 160 C and up
- Higher heat and longer exposure protein
- Dehydrates cell
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Thermal Death Time
TDT
Shortest length of time required to kill all microbes at a specified temperature
-
Thermal Death Point
TDP
Lowest temperature required to kill all microbes in a sample in 10 minutes
-
Moist Heat Control
- 1) Steam under pressure- (most efficient pressure temp 15psi and 121C, auto clave)
- 2) Non pressurized steam (treatment, incubation, treatment)
- 3) Boiling Water- (disinfection only, easily recontaminated, non spore forming pathogens)
- 4) Pasteurization- (Disinfection of beverages, 71.6 for 15 secs or 63-66 for 30 min. flash vs. batch)
-
Inineration
- Dry Heat
- 800 to 6500 C
- Reduces microbes, etc. by reducing to ashes and gases
-
Dry Oven
- usually electric
- 12min to 4 hours
- 150 to 180 C
-
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Irradiation
- Bombardment with radiation at cellular level
- Absense of heat, thus cold/ low temp sterilization
-
Ionizing Radiation
- penetrates solid barrier
- bombards cell
- breaks DNA and mutates
- Gamma rays, Xrays, high speed electrons
- Food, anthrax
-
Non Ionizing Radiation
- enters cells
- strikes molecules
- Effects DNA through abnormal bonds
- Disinfection for hospitals, schools, food prep
- Ultra violiet radiation
-
High Level Chemical Agents
Kills endspores and are sterilants
-
Intermediate Level Chemical Agents
Kills fungal spores and resistant pathogens
-
Low Level Chemical Agents
- Kills:
- Vegetative Bacteria
- Vegetative Fungal Cells
- Some Viruses
-
Halogens
Group VII
- exert in non ionic state
- Active ingredient in 1/3 of antimicrobial chemicals
-
Hypochlorites
- Halogen
- Extensive use
- santization and disinfection of food equipment, pools, spas, fresh foods
-
Chloramines
- Halogens
- Better/ safer than pure chlorine
-
Iodine
- Halogens
- Pungent blue and black chemical that forms brown-colored solutions
- Apps: disinfects burned and infected skin
-
Iodophors
- Halogen
- Used to prepare skin and mucus membrane
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