Sterilization, Disinfection and Antisepsis Flashcards Preview

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Flashcards in Sterilization, Disinfection and Antisepsis Deck (39)

Goal of disinfection/sterilization

-reduce the numbers of microorganisms on a device to a level that is insufficient to transmit infectious organisms


Healthcare-Associated Infections (HAI's)

-if you are admitted to a hospital, you have a 5% chance of contracting an HAI
-1.7 million people per year get an infection during a hospital stay
-your length of stay in the hospital increased by 17.6 days if you get an HAI
-over a quarter of all hospital-acquired HAIs are caused by four types of infections: pneumonia, bloodstream infection, surgical site infection, urinary tract infection


HAI's are associated with risk factors

-the use of indwelling medical devices such as bloodstream, endotracheal and urinary catheters
-transmission of communicable disease between patients and healthcare workers
-surgical procedures
-contamination of the healthcare environment
-overuse or improper use of antibiotics


Challenges with HAIs

-reprocessing of medical devices is a challenge with respect to HAIs
-endoscopes is probably the most challenging reprocessing tast in health care
-flexible endoscopes have intricate sophistricated small parts that are difficult to clean before they can be disinfected


History of Infection control

-Ignaz Semmelweis recommended chlorinated lime solution
-Florence Nightingal mortality rates in different wards
-Joseph Lister- clean wounds and dress them carbolic acid- first mostly sterile surgical field



results in the complete destruction of all forms of microbial life, including bacterial and fungal spores



-results in the destruction of specific pathogenic microorganisms- does not necessarily result in sterilization



-an agent is one that has been formulated for use on skin or mucous membranes to prevent or inhibit growth of microorganisms (Antiseptics should not be used to decontaminate inanimate objects)



-removal of debris, blood, and proteins- and most microorganisms- not necessarily rendering the decive "safe to handle" by HCW's who are not wearing protective attire


High-level disinfection (HLD)

-destroys all micro-organisms except high numbers of bacterial spores.
-example: pasteurization and liquid immersion in chemical sterilants (used for heat sensitive semi-critical items such as GI endoscopes, bronchoscopes)


Intermediate-level disinfection

-destroys vegetative bacterial, mycobacteria, most viruses, most fungi but not bacterial spores
-example: hospital disinfectant with label claim regarding tuberculocidal activity (e.g. chlorine-based products, phenolics-exposure times at least 30-60 seconds used on noncritical patient care items or surfaces with visible blood


Low-level disinfection

-destroys vegetative bacteria, some fungi and viruses but not mycobacteria or spores hospital disinfectant with no tuberculocidal claim (e.g. chlorine-based products, phenolics, quatemary ammonium compounds exposure times at least 30-60 sec) or 70-90% alcohol
-used on noncritical patient care items (e.g. blood pressure cuff) or surfaces (bedside table) with no visible blood


Factors that influence the degree of killing of microorganisms and the choice of disinfectant

-types of organisms
-number of organisms (bioburden)
-concentration of disinfecting agent
-presence of organic material (e.g. serum, blood)
-compatibility of disinfectants and sterilants
-nature of surface to be disinfected
-contact time


Critical items

-instruments or objects that are introduced directly into the bloodstream or into other normally sterile areas of the body


Semicritical items

-noninvasive flexible and rigid fiber optic endoscopes, endotracheal tubes, anesthesia breathing circuits and cystoscopes


Noncritical items

-those that either do not ordinarily touch the patient or touch only intact skin


Are the Microbes Dead of Not?

-cide or cidal:
Killing of the microorganism
-substances that kill microbes (pathogens and nonpathogens) but not necessarily their endoscopes
-static or stasis:
inhibit growth or multiplication of microorganism


Relative Resistance of Viruses and Bacteria to the Action of Disinfectants

Low to High Resistance:
Lipid enveloped viruses (HIV, HBV)
Gram-positive bacterial (S. aureus, entercoccus)
Large non-enveloped virus (Adenovirus)
Fungi (Candida, Aspergillus)
Gram-negative bacteria (Pseudomonas)
Trophozoites (Acanthamoeba)
Small non-enveloped viruses (Polio virus)
Cysts (Giardia)
Spores (Bacillus, C. difficile)
Coccidia (Cryptosporidium)
Priors (CJD, BSE)


Physical Methods of Microbial Control

-dry heat (hot air oven)- oil based
-moist heat- steam
-below 100 C- pasteurization
-at 100C- boiling
-above 100C autoclave

-UV radiation
-Ionizing radiation




-steam under pressue
-121C/15 psi for 15-90 mins
-132C/27 psi for 4-20 mins
-minimal time required
-loading and packing critical to performance

Immediate Use (Flash) Sterilization
-the process of sterilizing unwrapped instruments using steam for 3 minutes at 270 F at 27-28 psi
-not used for routine sterilization- used in OR



-does not achieve sterility but kills pathogens that might be present in mill, dairy products and beer: Myocobacterium, Salmonella
-classic: 63C 30 min
-Flash HTST 72C 15 s, rapid cooling
-UHT (ultra high temp) 140C for 1s then rapid cooling


Sterilization by Filtration

-excellent way to sterilize solution of heat-sensitive materials
-membrane filters (~0.1 mm thickness), Cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene, difluoride, other synthetic materials

-pore size 0.45 or 0.22 mm for bacteria
-0.01 mm for spirochetes, mycoplasma, viruses and large proteins

-use N95 mask



-ionizing radiation: shorter wavelength
-ex: gamma rays, x-rays, high energy electron beams
-ionixation of water forms highly reactive hydroxyl radicals
-uses: pharmaceuticals, disposable dental and medical supplies (syringes, gloves, sutures)

Nonionizing radation:
-UV rays: thymine dimers inhibit replication of DNA
-use in rooms with TB can be airbourne
-not penetrating
-damage human eyes, skin cancer, burns


Irradiated Blood Products and Food

-Irradiated RBC help to prevent graft versus host disease
-GVHD is a disorder where the grafted tissue attacks the host tissue by proliferation of T cells
-gamma radiation exposure prevents the proliferation of leukocytes especially T cells
-use of irradiation for food in the form of ionizing radiation destroys bacteria by damaging bacterial DNA
-prolongs the shelf-life of the food in cases where microbial spoilage is the limiting factor
-the treatment of hamburger eliminates the residual risk of a comtamination by E coli


Phenol and Phenolics

-exert antimicrobial activity by injuring plasma membranes, inactivate enzymes and denaturing proteins
-phenol (carbolic acid) - irritates skin disagreeable odor is now rarely used
-used for intermediate and low level disinfection


Hexachlorophene (pHisoHex)

-most active against gram positive bacteria
-toxic in newborns
-now used for staphylococcal skin decolonization in patients undergoing prosthetic or cardiac valve implant surgery



-is not a phenol derivative
-frequently used for disinfection of skin and mucous membranes- ChloraPrep
-used for surgical hand scrubs and preoperative skin preparation of patients
-low toxicity. Strong affinity to skin or mucous membranes
-killing effect by damaging plasma membrane
-effective against most vegetative bacteria but not sporicidal
-Disadvantages: genes conferring resistance observed in bacteria; allergies observed



-work by forming covalent crosslinks with a number of organic functional groups on proteins
-formalin: 37% aqueous solution of formaldehyde gas
-glutaraldehyde: used to sterilize hospital instruments
-less irritating more effective than formaldehyde
-Cidex (2% soln): bactericidal, tuberculocida, virucidal in 10 min; sporicidal in 3 to 10 hr
-is the only liquid chemical disinfectant that can be considered a sterilant


Gaseous Chemosterilizers

-ethylene oxide, propylene oxide
-denaturation of proteins by alkylation
-sterilize without heat
-sterilization of medical supplies and equipment: disposable plastic syringes, lensed instruments, artificial heart valves, heart-lung machine and mattresses
-Note: formaldehyde gas rarely used
-ETO is toxic, a carcinogen and flammable; requires aeration time to remove ETO residue


Quaternary Ammonium Compounds

-combined detergent and germicidal activity
-stable and working dilutions have low toxicity

-non sporicidal, limited activity against viruses, mycobaceria
-may support growth of bacteria

-surface decontamination- floor and walls
-equipment wipe down
-antiseptic formulations availible

Quarternary Ammonium Compounds- Topical uses
-Benzalkonium chloride: Zephiran (antisepsis of skin and mucous membranes and as a disinfectant)
-Cetylpyridinium chloride: Cepacol/ Colgate Total



-dehydrate cells, disrupt membranes and cause coagulation of protein
-may be used for hard surface disinfection or skin antisepsis
-types: Isopropyl alcohol and methyl alcohol and ethyl alcohol
-a 70% aqueous solution is more effective at killing microbes than absolute alcohols

-skin disinfectant (antiseptic)
-surface decontamination
-benchtop, cabinet wipedown

Advantage: good for intermediate and low level disinfection, inactivate most viruses with a lipid envelope

Disadvantage: cannot penetrate protein-rich materials, flammable



-single most important procedure for preventing nosocomial infections
-defined as a vigorous, brief rubbing together of all surfaces, followed by rinsing under a stream of water
-although various products are available, handwashing can be classified simply by whether plain soap or detergents
-hand sanitizers


Halogens: Iodine and Chlorine

-they are oxidizing agents and cause damage by oxidation of essential sulfydryl groups of enzymes
-chlorine reacts with water to form hypochlorous acid, which is microbicidal
-chlorine gas is used to bleach water
-household bleach can be used at a dilution of 1:10 in decontamination of spillage of infectious material
-disadvantage: unstable when diluted- needs to be made daily


Iodine Preparations

-tincture of iodine (2% iodine in 70% alcohol) is an antiseptic
-iodophore: iodine can be combined with neutral carrier polymers such as polyvinylpyrrolidone to prepare iodophores such as povidone-iodine
-iodophores permit slow release and reduce the irritation of the antiseptic
-Betadine, Isodine

Disadvantage: cannot be used to disinfect medical equipment unless at higher concentrations; commercial preparations are not sporicidal at the dilutions recommended for use


Heavy Metals and Organic Acids

-metal ions combine with SH groups on proteins
-heavy metals: silver nitrate (1% for ophthalmic preparations); merchurochrome (mercury); copper sulfate; zinc chloride; zinc oxide
-organic acids and derivatives- sorbic acid; benzoic acid; methylparaben; propylparaben


Hydrogen Peroxide

-acts on the microorgnisms through its release of nascent oxygen. Hydrogen peroxide produces hydroxyl-free radical that damages proteins and DNA
-used at 6% concentration to decontaminate instruments and equipment such as ventilators
-3% Hydrogen Peroxide Solution is used for skin disinfection and cleaning of wounds and ulcers
-strong solutions are sporicidal
-disadvantages: decomposes in light, broke down by catalase, proteinaceous organic matter drastically reduces its activity


Peracetic Acid

-a mixture of acetic acid and hydrogen peroxide in an aqueous solution
-PAA disinfects by oxidizing of the outer cell membrane of vegetative bacterial cells, endospores, yeast and mold spores

-peracetic acid can be used as a cooling tower water disinfect where it prevents bio film formation and effectively controls Legionella bacteria
-peracetic acid is extremely effective for sanitizing fowl carcasses without affecting the skin or the flesh of the bird by applying direct to the meat
-plasma (gas phase) sterilization


Plasma sterilization

-beneficial for sterilizing temperature sensitive polymeric material-such as endoscopes
-provides safe non-toxic dry, low temp sterilization in about 1 hr
-gas plasma is generated in an enclosed chamber under deep vacuum using UV or microwaves to create free radical in a gaseous phase

Vacuum applied -> H2O2 or PAA injected which beomces gas -> UV/MW applied free radicals formed -> bacteria killed -> activated radicals lose energy and form water


STERRAD Sterilization System

-uses low temperature, hydrogen peroxide gas plasma technology to sterilize instruments and medical devices
-quick instrument reprocessing
-express cycle for da Vinci 3;D endoscopes and other devices without lumens
-processes a wide range of instruments including multiple single-channel flexible endoscopes, cameras, rigid scopes, light cords, batteries, and power drills