Transcript Continues

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
Introduction
─Contaminated
─Infection
─Inflammation
─Nosocomial infection (HAI)
─Cleaning
─Sanitation
─Decontamination
─Disinfection
─Sterilization
4-4
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
4-5
Methods Used to Disinfect and Sterilize
•
•
•
•
•
•
•
Heat
Pasteurization
Boiling water
Steam and pressure
Liquids and compounds
Gas sterilization
Radiation
4-6
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)
4-7
Heat
• Moist heat
– Steam
– More effective if pressurized (autoclave)
• Incineration
– Destroys and thus sterilizes objects
4-8
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
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
Steam and Pressure
• Disadvantage of autoclave
– Cannot be used for oils, waxes
– May melt plastic or rubber
– May corrode metals
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, gramnegative, 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