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 dioxide –gas (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! |
