1. STERILIZATION AND DISINFECTION
CHAPTER 12
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2. Aseptic Principles Sterilization Disinfection Disinfectants
Antiseptics
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4. Controlling Microbial Growth
Proportional Death rates
Time required for sterilization
Initial microbial numbers
Role of organic matter
Cleanliness
Microbial susceptibilities
Physiology
Cell wall molecules
Resistances due to enzymes
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5. Chemical Antimicrobials
Effects on potency
Time
Temp pH
Concentration
Bacteriocidal
Bacteriostatic
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6. Evaluating Effectiveness
Phenol Coefficient
Salmonella and Staphylococcus
Filter Paper Method
Disc Diffusion
Use Dilution Assay
Stainless steel cylinders coated in bacteria
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8. Disinfectant Selection Criteria
Fast-acting
Stable around organics
Non-toxic
Wide spectrum
Non-damaging to materials
Easy tp prepare
Stable
Readily available
Inexpensive
No offensive odor
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9. Mechanisms of Action Effects on Proteins Effects on Membranes (lipids)
Surfactants
Non-polar substances
Effects on Nucleic acids
Alkylating agents
Virus susceptibilities
Enveloped vs. non-enveloped
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10. Classes of Disinfectant
Soaps/ detergents
Soaps
Limited effectiveness, dirt dispersal
Quaternary ammonium detergents
Pseudomonas not killed
Tinctures are more effective
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11. Disinfectant Types Acids/Alkalis Food industry uses organic acids
Lactic/propionic –molds in bread
Benzoic - molds in ketchup, sodas, margarine
Sorbic acid – molds in cheese
Heavy Metals
Ag, Cu, Hg
Denature enzymes
Halogens
Chlorine (disinfectant)
Iodine (antiseptic)
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12. Classes of Disinfectant
Phenolics
Work in heavy organic contamination
Chlorinated phenolics more effective
Hexachlorophene (Staphylococcus) use limited in newborns
Alcohols
Isopropanol less regulated
Evaporation means little contact with microbes
No residue
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13. Oxidizers H2O2 Potassium permanganate Ozone Unstable on tissues
Kills anaerobes in puncture wounds
Potassium permanganate
Used on instruments and skin
Ozone
Used in water treatment as chlorine alternative
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14. Physical Agents - Heat Dry Heat Ovens Flaming Moist Heat Steam
Autoclave
Pasteurization
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15. Use of Low Temperatures
Refrigeration/Freezing
Limited to few days
Psychrotrophs survive
Dessication
Bacteriostatic only
Freeze-drying
Bacteriostatic
Used to preserve cultures
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16. Irradiation Ultraviolet light Ionizing radiation X-rays Gamma Rays
Microwave radiation
Visible light
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17. Additional Disinfection Methods
Sonication
Filtration
Air / Water
0.3um average pore size
HEPA
0.1um for viruses
Osmotic Control
Dessication
Sugaring/ Salting
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