Sterilization and Disinfectants – Flashcards

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Sterilization: Physical Agents (Moist Heat)

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Physical Agents -
Moist heat – uses an autoclave that introduces steam under pressure
-Most effective, practical method
-Most hospitals use it as a first choice method of sterilization
-Not applicable to heat-labile substances (ie., antibody solution, antibiotics)
-The steam must be able to penetrate in order to sterilize the material (container cannot be sealed; petroleum jellies not penetrated)
-Inactivates life forms by denaturation/coagulation of biological molecules; steam is the killing agent
-Process sterilizes more quickly than dry heat
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Sterilization: Physical Agents (Dry Heat)

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Dry heat
-Inactivates life forms by oxidation/denaturation
-Does not dull sharp edges, unlike autoclaving
-Can sterilize closed containers and oils/petroleum jellies, which are not penetrated with steam
-Takes longer to sterilize than autoclaving

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Sterilization: Ultraviolet Radiation

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-Radiation
Ultraviolet radiation
-Damages DNA & inhibits its replication
-Most effective against airborne microorganisms
-Often used to prevent airborne spread of bacteria in hospitals, microbiology labs, etc.
-Poor penetration
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Sterilization: Ionizing Radiation

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Ionizing radiation
-Beta rays (electron) or gamma rays
 ‘Chain reaction’ where bacterial/viral cell components absorb electrons, then give off high energy electrons, disrupting cell components
- Sutures, plastic tubing, plasticware
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Sterilization: Filtration

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-Filtration
-Used for solutions that are heat labile or whose efficacy/safety is compromised by the introduction of chemicals or heat (i.e., antibiotics/antibody solutions)
-Solution is filtered through a membrane that retains bacteria, fungi, algae
-Does not always remove viruses (depends on pore size – for example 0.2 micron filter will not remove some viruses) – therefore not ‘sterilization’ in the strictest sense (Not FDA-approved sterilization method)
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Sterilization: Chemical Agents

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Ethylene oxide (gas, slow) alkylates
-Useful for delicate instruments, optics
-Flammable, explosive and carcinogenic so use has been curtailed
Glutaraldehyde (liquid solution, 2%) alkylates Inhibited by dirt
 Hydrogen peroxide solution (>10%) or plasma – oxidizes
Plasma: hydrogen peroxide plasma that has been microwaved to increase available oxygen radicals, which are the killing agent
Chlorine dioxidegas (used to decontaminate buildings where anthrax attacks occurred); oxidizes
Peracetic acid (liquid solution) oxidizes
-Preferred method of sterilizing heat-sensitive instruments at LSUHSC.
-By products are non-toxic (acetic acid and oxygen)
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Spaulding Scheme

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Critical Items – items that enter tissue, blood; example: surgical items, cardiac catheters, implants
-Items that would be dangerous if contaminated with spores
-ALWAYS sterilize!  Any life forms present a high degree of risk
 Semicritical items – items that come into contact with mucous membranes;    example:  endoscopes
-Items that do not present such a high risk if contaminated by a small amount of spores but should not be contaminated with bacteria/viruses
Sterilize OR use high level disinfectant
 
Noncritical items – blood pressure cuffs, crutches, bed rails, floors
-May come in contact with intact patient skin
-Low or medium level disinfection
 
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Disinfection: High Level

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High level:  (used mostly on semicritical items; some overlap with sterilants; all high level methods may be sporocidal)
 
-Glutaraldehyde (2%) – liquid - Alkylates cell components.  BURNS!
 
 
 
 
 
 
 
-Peracetic acid (0.2%) – liquid - Oxidizes cell components
-Chlorine dioxide – Oxidizes, liquid or gas (also a sterilant) TOXIC!
-Hydrogen peroxide (>10%) – liquid or plasma - Oxidizes cell components
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Disinfection: Intermediate Level

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Intermediate level (used mostly on noncritical items; either weakly sporocidal or nonsporocidal)
-Alcohols – denature proteins – inhibited by dirt!  Some used as antiseptic.
-Sodium Hypochlorite (bleach) – inhibited by alkaline pH (i.e. alkaline detergents).  Stronger bacteriocidal/virucidal/sporacidal activity at higher concentrations (can be high or low level disinfectant)
-Iodophor compounds – denature/oxidize proteins – not influenced by pH – inhibited by dirt.  Some used as antiseptic.
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Disinfection: Low Level

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Low level – noncritical items (not sporicidal; do not inactivate all bacteria/viruses)
 
 
 
 
 
 
 
 
 
Quaternary ammonium compounds – denature cell membranes; precipitate biological molecules.
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Chlorhexidine 

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Chlorhexidine: surgical scrub, medicated soap, mouthwash

-Disrupts membranes/lipids
- Activity persists after drying
- Poor killing activity against some Enterocococcus,

  Staphylococcus species.

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Triclosan

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Most common ingredient in antibacterial soaps, other common antibacterial products (soaps, deodorants, toothpaste, socks!)

 

Inhibits a specific bacterial enzyme: bacterial enoyl-acyl carrier protein reductase enzyme.
 

 

 
Effects on virus unknown!
 
Bacterial resistance?  Though effective in laboratory settings, efficacy in households/clinical settings uncertain.
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Alcohol

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Alcohol gels: best choice for routine hand antisepsis.
-Fast acting
-Broad spectrum killing
-Increased compliance over handwashing!
-Use has decreased NI!
-Hands need to be free of dirt before using!

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