1. CHAPTER 4
Infection Prevention

2. Introduction
Infection prevention terminology is required for understanding microbiology in practice
Infection prevention
Chain of infection
Vegetative organisms
Spores
Denatured
(Continues)
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3. Introduction Contaminated Infection Inflammation
Nosocomial infection (HAI)
Cleaning
Sanitation
Decontamination
Disinfection
Sterilization
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4. Issues to Consider When Killing an Organism
Number and type of organism (determines methods/procedures used)
Type of agent for infection control
Strength of the killing agent
Amount of exposure time required
Environmental issues, such as temperature
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5. Methods Used to Disinfect and Sterilize
Heat
Pasteurization
Boiling water
Steam and pressure
Liquids and compounds
Gas sterilization
Radiation
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6. Heat
Commonly used
Higher temperatures require less time for disinfecting/sterilizing procedure
Denatures proteins, leading to cellular coagulation
Dry heat
For objects that could be damaged by moist heat (oils, powders, dressings)
Often used for glass
(Continues)
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7. Heat Moist heat Steam More effective if pressurized (autoclave)
Incineration
Destroys and thus sterilizes objects
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8. Pasteurization Heated water Kills vegetative cells
Denatures most viruses
If using for instruments
Immerse instruments in 70˚ C water for 30 minutes; dry; package in a sterile manner
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9. Boiling Water Kills most bacteria
Inactivates most viruses in 15 minutes
Not true sterilization process; is ineffective against many bacterial and fungal spores
Altitude effectiveness (for every 1,000-foot increase in altitude, increase boiling time by 5 minutes)
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10. Steam and Pressure Most effective sterilization method
Autoclave combines use of steam and pressure
Autoclave use
Package items with heat-sensitive indicator; determines sufficient sterilization
Kills bacteria, fungi, spores
Denatures viruses
(Continues)
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11. Steam and Pressure Disadvantage of autoclave
Cannot be used for oils, waxes
May melt plastic or rubber
May corrode metals
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12. Liquids and Compounds Alcohol Acetic Acid Phenols Chlorine
Hydrogen peroxide
Quaternary ammonium compounds
Glutaraldehydes
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13. Alcohol Disorganizes lipid structures of cell membrane
Denatures cellular proteins
Effective against gram-positive, gram-negative, and acid-fast bacteria
Not sporicidal
May irritate skin
(Continues)
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14. Alcohol May damage plastic or rubber Two forms
Ethanol (ethyl alcohol)—most effective at 70% concentration
Isopropyl alcohol—most effective at 90% concentration
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15. Acetic Acid Vinegar Used as food preservative
Inhibits growth of many bacteria and fungi
Acidity denatures cell’s proteins
White distilled vinegar (preferred)
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16. Phenols Cause cell leakage Inactivate enzymes in cell membrane
Virucidal
Not sporicidal
Most common use: cleaning instruments and general housekeeping
Avoid skin contact
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17. Chlorine Gaseous and liquid form
Effective against most bacteria, viruses, fungi
Not sporicidal at room temperature
Highly corrosive to some metals
Cannot be used on rubber
Hexachlorophene: chlorinated disinfectant without chlorine smell
(Continues)
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18. Chlorine 1:10 solution Recommended to clean blood spills 1:50 solution
Effective against gram-negative bacteria, bacterial spores, Mycobacterium tuberculosis with 10-minute exposure time
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19. Hydrogen Peroxide 3% solution Mild antiseptic for wound cleaning
Stronger than 3% may cause wound tissue damage
6% solution
Bactericidal, virucidal, fungicidal with 10-minute exposure at room temperature
Sporicidal if 6-hour exposure
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20. Quaternary Ammonium Compounds
Cause loss of semipermeability by cell membrane leading to lysis and denaturing of cell’s proteins
Bactericidal (especially gram positive)
Ineffective against bacterial spores, enteroviruses, hepatitis B, some fungi, and spores causing TB
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21. Glutaraldehydes
Soaks used for disinfecting/sterilizing surgical instruments/equipment
Bactericidal, tuberculocidal, fungicidal, virucidal with 10- to 30-minute exposure
Sporicidal with 10-hour exposure time
Action: interruption of metabolism and reproduction of microorganism
(Continues)
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22. Glutaraldehydes Irritate skin, mucous membranes, eyes
Can damage rubber and plastic
Can damage steel
Require rinsing, drying, and proper packaging of items after soaking procedure completed
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23. Gas Sterilization Ethylene oxide (ETO)
Interrupts metabolism and reproduction of organisms
Sterilization depends on
Gas concentration
Humidity
Temperature
Time
(Continues)
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24. Gas Sterilization
Requires indicator tape placement in package (does not guarantee sterility)
Requires use of biological indicator daily (if sterilization is effective, bacteria culture dies)
Requires 24-hour air time in well-ventilated area
May be toxic to humans
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25. Radiation Ultraviolet rays Bactericidal action Damage DNA
Mercury vapor lamps disinfect operating rooms and nurseries
(Continues)
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26. Radiation Gamma irradiation Highly efficient short wavelength of light
Ionizes water molecules
Inactivates DNA molecules
Does not generate excessive heat
Items can be prepackaged and sealed
Requires 48–72 hours
May release chlorine gas
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27. Summary Goal is to prevent infection from ever occurring
Once infection has occurred, the goal is to break the chain of infection
Methods of disinfection/sterilization include heat, pasteurization, boiling water, steam and pressure, liquids and compounds, gas sterilization, and radiation
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