Sterilization, Disinfection and Antisepsis Flashcards
1
Q
Goal of disinfection/sterilization
A
-reduce the numbers of microorganisms on a device to a level that is insufficient to transmit infectious organisms
2
Q
Healthcare-Associated Infections (HAI’s)
A
- 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
3
Q
HAI’s are associated with risk factors
A
- the use of indwelling medical devices such as bloodstream, endotracheal and urinary catheters
- transmission of communicable disease between patients and healthcare workers
- surgical procedures
- injections
- contamination of the healthcare environment
- overuse or improper use of antibiotics
4
Q
Challenges with HAIs
A
- 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
5
Q
History of Infection control
A
- 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
6
Q
Sterilization
A
results in the complete destruction of all forms of microbial life, including bacterial and fungal spores
7
Q
Disinfection
A
-results in the destruction of specific pathogenic microorganisms- does not necessarily result in sterilization
8
Q
Antisepsis
A
-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)
9
Q
Decontamination
A
-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
10
Q
High-level disinfection (HLD)
A
- 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)
11
Q
Intermediate-level disinfection
A
- 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
12
Q
Low-level disinfection
A
- 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
13
Q
Factors that influence the degree of killing of microorganisms and the choice of disinfectant
A
- 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
- temperature
- pH
- biofilms
14
Q
Critical items
A
-instruments or objects that are introduced directly into the bloodstream or into other normally sterile areas of the body
15
Q
Semicritical items
A
-noninvasive flexible and rigid fiber optic endoscopes, endotracheal tubes, anesthesia breathing circuits and cystoscopes
16
Q
Noncritical items
A
-those that either do not ordinarily touch the patient or touch only intact skin
17
Q
Are the Microbes Dead of Not?
A
-cide or cidal: Killing of the microorganism Germicides -substances that kill microbes (pathogens and nonpathogens) but not necessarily their endoscopes -bactericide -fungicide -virucide -amoebicide -static or stasis: inhibit growth or multiplication of microorganism
18
Q
Relative Resistance of Viruses and Bacteria to the Action of Disinfectants
A
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)
19
Q
Physical Methods of Microbial Control
A
Heat:
- incineration
- dry heat (hot air oven)- oil based
- moist heat- steam
- below 100 C- pasteurization
- at 100C- boiling
- above 100C autoclave
Radiation:
- UV radiation
- Ionizing radiation
Filtration
20
Q
Autoclaving
A
- 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
21
Q
Pasteurization
A
- 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
22
Q
Sterilization by Filtration
A
- 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
23
Q
Radiation
A
- 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
24
Q
Irradiated Blood Products and Food
A
- 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
25
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
26
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
27
Chlohexidine
- 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
28
Aldehydes
- 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
29
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
30
Quaternary Ammonium Compounds
Advantages:
- combined detergent and germicidal activity
- stable and working dilutions have low toxicity
Disadvantages:
- non sporicidal, limited activity against viruses, mycobaceria
- may support growth of bacteria
Uses:
- 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
31
Alcohols
- 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
uses:
- 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
32
Handwashing
- 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
33
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
34
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
35
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
36
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
37
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
Uses:
- 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
38
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
39
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
