CHAPTER 4 Infection Prevention 4-2

Introduction Infection prevention terminology is required for understanding microbiology in practice ─Infection prevention ─Chain of infection ─Vegetative organisms ─Spores ─Denatured (Continues) 4-3

─Contaminated ─Infection ─Inflammation ─Nosocomial infection (HAI) ─Cleaning ─Sanitation ─Decontamination ─Disinfection ─Sterilization Introduction 4-4

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 Issues to Consider When Killing an Organism 4-5

Heat Pasteurization Boiling water Steam and pressure Liquids and compounds Gas sterilization Radiation Methods Used to Disinfect and Sterilize 4-6

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) Heat 4-7

Moist heat –Steam –More effective if pressurized (autoclave) Incineration –Destroys and thus sterilizes objects Heat 4-8

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 Pasteurization 4-9

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) 4-10

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) 4-11

Disadvantage of autoclave –Cannot be used for oils, waxes –May melt plastic or rubber –May corrode metals Steam and Pressure 4-12

Liquids and Compounds Alcohol Acetic Acid Phenols Chlorine Hydrogen peroxide Quaternary ammonium compounds Glutaraldehydes 4-13

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) 4-14

Alcohol May damage plastic or rubber Two forms –Ethanol (ethyl alcohol)—most effective at 70% concentration –Isopropyl alcohol—most effective at 90% concentration 4-15

Acetic Acid Vinegar Used as food preservative Inhibits growth of many bacteria and fungi Acidity denatures cell’s proteins White distilled vinegar (preferred) 4-16

Phenols Cause cell leakage Inactivate enzymes in cell membrane Virucidal Not sporicidal Most common use: cleaning instruments and general housekeeping Avoid skin contact 4-17

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) 4-18

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 4-19

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 4-20

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 4-21

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) 4-22

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 4-23

Gas Sterilization Ethylene oxide (ETO) Interrupts metabolism and reproduction of organisms Sterilization depends on –Gas concentration –Humidity –Temperature –Time (Continues) 4-24

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 4-25

Radiation Ultraviolet rays –Bactericidal action –Damage DNA Mercury vapor lamps disinfect operating rooms and nurseries (Continues) 4-26

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 4-27

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 4-28