Unit 8: sterilization, antiseptics and disinfectants Flashcards
Sterile means
No living microorganisms are present
Asepsis means
No pathogenic organisms present
All things within an operating room fall into 1 of 4 categories
Sterile
Aseptic
Clean
Contaminated
What does aseptic mean when it comes to objects
the absence of pathogenic microorganisms that can cause infection
A portion of a living creature has been rendered as free as possible of all pathogens is surgically clean
The incision site and the surgeons hands become surgically clean using antiseptic soaps and solutions and by the scrubbing motion
What does clean mean in terms of surgical objects
An object or surface that has been disinfected and has not been knowingly exposed to any pathogens
This is accomplished using a disinfectant and the scrubbing motion
What does contamination mean
An object, animate or inanimate, that is known to harder pathogens
What does aseptic technique mean
Aseptic technique includes all steps taken to prevent contamination of the surgical site by infectious agents
Properly sterilizing surgical equipment
Cleaning the operating room
Scrubbing and draping
What are the sources of contamination
Exogenous route
- Air
- Surgical supplies
- Patients skin
- Surgical team
Endogenous route
- Bacteremia: through the bloodstream
Risk of infection doubles every hour under general anaesthesia
What does clean mean in terms of type of surgery
No break in asepsis during surgery. The GI, resp and urinary tract are not entered
What does clean contaminated mean in terms of surgery
A contaminated area such as the genital, urinary or resp tract has been entered with no spread of contents
What does contamination mean in terms of surgery
No infection is present but there is spillage of viscera contents
What is a dirty surgery
Major break in asepsis. Surgery that is infected or contaminated
What does sterilize mean
The complete destruction or removal of all microorganisms and their pathogenic products
What does disinfect mean
Destruction or removal of vegetative pathogens but not bacterial endospores. Usually referring to an inanimate object
What does disinfectant mean
Chemical applied to inanimate objects to destroy or inhibit vegetative pathogens. Chemicals are typically too harsh to use on living tissue
What does antiseptic mean
Chemical applied to body surface to destroy or inhibit vegetative pathogens
What is sterilization and what does it refer to
Sterilization is the process of destroying all microorganisms and their pathogenic products (endotoxin and exotoxin)
Does NOT refer to prions (which are abnormal proteins) and may not destroy all plasmids
Used to maintain asepsis: both to prevent contamination and to destroy contaminants
Items that have need sterilised are “sterile”
What are the main methods of sterilization
Sterilization by heat (moist heat or dry heat)
Chemical sterilization
Ultrafiltration
Ionizing radiation
What is steam sterilization and what does it clean
An item is subjected to moist heat, at a predetermined temperature, under a predetermined pressure, for a predetermined length of time
Microbes are destroyed by coagulation of proteins also damages nucleic acids, etc
Destroys spores
Destroys prions
How does autoclaving work
Placing steam under very high pressure to increase temp to approx 120*C
Pressure does not increase the killing effect but causes more heat to be required for water to boil
Typical pressures in an autoclave are 20 psi (pounds per square inch)
Can range from tabletop models to large full room units
What are the components of an autoclave
Airtight door with bolting mechanism to hold in pressure
Metal chamber for holding materials to be autoclaved
Steam source
Steam exhaust
Pressure and temp gauges
how long does an autoclave take to clean
It takes about 20 minutes for an object to be sterilized
Can be used to sterilize liquids, wrapped and unwrapped materials
What are precautions to take when autoclaving
Pack materials loosely so steam can access each item
Containers with liquids
- Caps must be loose, or bottles will explode
- Cannot fill to top as they will boil over
- Place bottles in tray to catch spills
- Allow pressure at the end of the cycle to release slowly or there is risk of boiling over, overexpansion or explosion
Always open the door a gap (with bolts still engaged). This allows pressurized steam to escape from the chamber slowly. Rapid release can cause severe burns
Never autoclave alcohols, bleach, acids, formalin…anything noxious or flammable
What quality control measures do you take for autocalves
Indicators
Autoclave tape
Fusible melting pellet glass
Culture tests
Chemical indicators
Air removal test (pre vacuum sterilizers)
Care and handling
Sterile packs should be stored in a dust free, dry, well ventilated area away from contaminated equipment
How is autoclave tape helpful
Placed on the outside of an autoclaved pack or container
Tape changes colour as soon as it is exposed to 121*C
Does not indicate how long it was exposed to that temp so it should not be sued as the only indicator of sterility
How do steam chemical indicator strips work
Strips of paper with a chemical pellet that melts after reaching a certain temp for a certain amount of time
As the pellet melts, a dark dye wicks along the strip of paper. It must reach the end of the strip to be “accepted”
Strips should be placed in the center of EACH individual pack and the center of the loaded autoclave to ensure sterility
How does a biological indicator work for autoclave quality control
A commercially prepared vial containing Bacillus stearothermophilus spores (which are killed at 121C in 12 minutes) is paced in the center of an autoclave load. After autoclaving, contents of the vial are cultured at 56C for up to 3 days to see if there is growth
Used as quality assurance for the autoclave machine. Should be run periodically to ensure machine is working properly
How and when do you use flash sterilization
Used when an item is required immediately
Once the autoclave has reacher 120*C the load is timed for 3 min
After that time, the autoclave is shut off, set on rapid exhaust and the drying cycle is skipped
After sterilization, allow packs to cool slowly
What are the types of chemical sterilization
Liquid sterilization
- Glutaraldehyde
Gas sterilization
- Ethylene oxide
- Plasma sterilization
Aldehyde
- Formaldehyde and glutaraldehyde
- Toxic and irritating
- Antimicrobial
Cold sterilisation
- Soaking instruments in disinfecting solutions (chlorhexidine or glutaraldehyde)
- Used only for minor procedures or equipment that cannot tolerate other sterilization methods
- Must be rinsed thoroughly with sterile water under aseptic conditions (sterile gloves)
How does ethylene oxide work
Flammable, explosive, toxic
Penetrates paper and plastic packaging without melting it
- Wrapped in plastic packaging, sealed
Temp versus time
- 3-4 hours at room temp, humidity must also be controlled
Quarantine is well ventilated area for a min of 24 h, time can be reduced to 4 h in an aerator
What is plasma sterilization and what is it not safe for
hydrogen peroxide
Safer for enviro and personnel than ethylene oxide
Not safe for
- Linen
- wood/paper
- Endoscopes
- Certain plastics
- Liquids
- This method cannot penetrate the walls of instruments so the lumen will remain contaminated
How do disinfectants and antiseptics work
Antiseptics and disinfectants work by
- Damaging the cell membrane
- Interfering with or damaging proteins
- Damaging DNA and/or RNA
The strength of a disinfectant (how well it works) is measured by a value called the Phenol Coefficient or Co-efficent of disinfectant
- The higher this number the better ability to kill microbes
How do enveloped viruses work
Steal a piece of host cell membrane when they leave infected host cell – this envelope surrounds the virus particle
If this envelope is disrupted, the virus is destroyed
Non enveloped viruses
Do not have any phospholipids (usually smaller pieces of genetic material in protein capsule) resistant to chemicals that damage cell membrane
Why are some chemicals limited in their functions
Chemicals that work by destroying cell membranes are limited in their ability to kill spores and certain viruses
Spores do not have cell
Membranes
Viruses can be broadly categorized as enveloped and non-enveloped viruses.
What are the conditions of the ideal disinfectant
Has a good coefficient of disinfection
Good killing action at low concentration
Broad spectrum
Vegetative bacteria and fungi; bacteria; endospores and fungal spores; enveloped and non enveloped viruses
Stable
Can be stored for long periods of time without losing effectiveness
Can store at room temp, in the presence of light and air
Homogeneous
Uniform in composition; every application acts the same
Soluble
Soluble in water → makes it more effective to use (can spread, wipe, immerse)
Non toxic to animals and people
Non corrosive, non bleaching, non staining, not flammable
Works at room temp
High penetration of biofilms and fat
Phenol very effective with fat;bleach is not
Detergent ability
Both cleans and disinfects; the ability to clean will help to penetrate fats, grime, biofilms
Is not neutralized by organic material that may be present
Ease of use
Affordable and readily available
Deoderizing
What are the characteristics of ethanol
Most commonly used at 70% v/v dilution
Kills all vegetative cells, including Mycobacterium
Does not destroy spores, kills some (not all) viruses
Dissolves lipids, dentures proteins, does not damage nucleic acids
There must be contact time, so apply alcohol and allow to evaporate on own
Has decreased efficacy at higher temp due to faster evaporation
Ethanol is NOT effective at 95-100% due to rapid evaluation
What are the advantages of ethanol
Cuts through fat and lipids
Inexpensive, readily available
Can use on skin, on inanimate surfaces, for soaking → both a disinfectant and an antiseptic
Comes in a hand gel format that includes surgical strength hand cleaners (must follow manufacturer’s directions for surgical asepsis)
What are the disadvantages of ethanol
Will cause cooling when applied to skin
Can be absorbed causing alcohol intoxication – especially in small animals and pediatrics
Flammable, explosive
Damages plastics and rubber
What are the characteristics of isopropyl alcohol
2-propanol
Used at 70% v/v dilution (aka rubbing alcohol)
As effective as ethanol, especially of fortified with iodine or another disinfectant
Cheaper and more easily obtainable than ethanol
Quaternary ammonium compounds work how
Commonly used disinfectants; contains ammonia
Disrupts cell membranes and denatures protein
What is the range of activity for Quaternary ammonium compounds
Broad spectrum against bacteria
Effective at destroying enveloped viruses
What are the older generations of QUATs not good against
Non enveloped virus
Some Pseudomonas resistance
Mycobacterium
Spores
What are the advantages of QUATs
Stable, dissolves easily in water
Odorless, does not stain, not corrosive
Effective i n pus, blood, feces
Inexpensive
What are the disadvantages of QUATs
Can cause slight injury to tissue
Should never be mixed with soaps (will decrease efficacy)
Decreased activity in hard water
Older generations require long contact times (10-20 min)
What are oxidizing agents
Hydrogen peroxide (Peroxigard™)
Hypochlorites
Potassium peroxymonosulfate (Virokon®)
How does hydrogen peroxide work and against what
Very commonly used
Hydrogen peroxide forms free-oxygen radicals
These are very reactive oxygen molecules that can damage cell membranes, mitochondria and other cell components
Activity
Broad spectrum
Non enveloped viruses
Can destroy spores at very high concentration
If concentration is too low, catalase producing bacteria may have some resistance
What are the advantages of hydrogen peroxide
Decomposes to water and oxygen
Inexpensive, easy to use aqueous solution
Can be vaporized and used for “gas sterilization”
Objects are placed in a chamber and gassed with a hydrogen peroxide compound
Good for glass, metals, certain equipment
What are the disadvantages of hydrogen peroxide
Decomposes in the presence of light, metals, oxygen
New formulations are stable for months in storage
How does hypochlorites work
Chlorine containing agents
Most common → sodium hypochlorite (bleach)
Denatures protein
The chlorine combines with water to release hypochlorous acid (HOCL)
During reaction, any surrounding cysteine residues and S-S bonds are destroyed
Broad spectrum including bacteria, fungi, spores and all types of viruses
Acts within 30 min; spores may take hours
What are the cautions with hhpochlorites
Concentrated solutions will rapidly release chlorine gas
Never mix with acid → will produce toxic chlorine gas
Never combine with Quats → will produce toxic chloramine gas
Caustic effects to skin and mm, especially at higher concentrations
How does sodium hypochlorite work
Concentrated sodium hypochlorite is 20% w/v
Household bleach is 5.25% w/v sodium hypochlorite
To use as a disinfectant, use a 10% solution of household bleach
Corrosive → must be rinsed afterwards
Be careful of fumes when using concentrated sodium hypochlorite
Area must be well ventilated
Avoid spills
How does potassium peroxymonosulfate work
Oxidizing agent with detergent action
- Oxidizes sulfur bonds in proteins and enzymes disrupting the function of the cell membrane causing rupture of the cell wall
Broad spectrum bacteria, fungi, most viruses (incl. parvo)
- Not spores
Comes as a tablet that makes a 1% solution in water
- 7 day shelf life once made (must write date made)
Requires 10 min of contact time followed by rinsing
Disinfecting hard surfaces, including food bowls, cages, kennels
Can also use as aerosol if concerned about air contamination
Low toxicity but avoid direct skin use
Why arent phenols used in clinics
Infrequently used in the vet clinic as they can cause toxicities in cats
Chlorhexidine gluconate is and used for
Antiseptic that is related to the Quats
Mild, low toxicity, rapid acting, poor absorption
Complex organic molecules that dissociates into a positively charged salt
This salt binds to and disrupts negative charges associated with bacteria cells walls
Low concentrations: static
High concentrations: cidal
Broad spectrum against bacteria, yeast and some viruses
No action on spores
Antiseptic of choice for MRSA
what strengths are chlorhex availible in
Chlorhexidine are available in strengths ranging from 0.05% to 4%
Higher concentration will cause tissue damage and delayed wound healing
Intact skin with stand a higher concentration than wounds
What are the 2 available formulas for chlorhexidine
Aqueous formulas
- Do NOT have alcohol
- Safe for use around eyes and for flushing of wounds
Solutions continuing alcohol
- NOT safe around the eyes and will cause damage to wound and healing tissue
How and when is iodine used
Antiseptic
Broad spectrum bactericidal
(may be less effective than chlorhexidine – Jarral et al., 2011)
Used at a 2-2.5% solution
Can be purchased as
A water (aqueous) solution
A “tincture”
2.0-2.5% iodine in 70% ethanol
More effective because can cut through lipid
Used for cleaning cuts, wounds, surgical prep
Apply a single coat to skin and allow to air dry
AVOID eye contact
Do NOT allow to pool under patient on a surgery mat
Will cause burns if prolonged contact with solution
What are iodophors and how do they work
Iodine that is loosely bound to a detergent (such as povidone) that releases it slowly and cuts through organic matter
Prolonged effect after applied to skin
Not irritating to the skin; but can have mild hypersensitivity and will discolor skin
Povidone-iodine is most common (betadine, Losan)
Surgical scrubs (esp. In LA), teat dips
