MIIM - Sterilisation, Disinfection, and Infection Control - Week 8 Flashcards
Define aseptic technique.
Using procedures that minimise the transfer of micro-organisms.
Define infection control.
Involves the prevention or minimisation of cross infections.
Define cross infection (3).
The spread of micro-organisms from patient to staff, staff to patient, and patient to patient.
List 5 risk factors for spreading infection in an optometric setting.
Removing foreign bodies
Assessing patients with ocular trauma or infection
Carrying out lacrimal lavage
Expressing glands and cysts
Fitting contact lenses
Briefly mention some diseases that can be passed from patient to optometrist (13).
HIV
Hepatitis B and C
Measles
Mumps
Rubella
Varicella
Glandular fever
Herpes
Influenza
Adenovirus 8
CJD
Define cleaning.
Removal of contaminating matter to lower the burden of organic material
Define disinfection.
Removing from an article some or all of its pathogenic micro-organisms
Define sterilisation.
Destruction or removal of all viable micro-organisms, spores, and other infectious agents from an article
Define and describe the three categories of the spaulding classification system.
Critical - invasive devices that enter normally sterile tissue or the vascular system by intent or accident
Semi-critical - device contacts, but does not penetrate, mucous membranes
Non-critical - device only contacts skin
Describe how to determine the initial contamination level of a sample.
Serially dilute the sample, spread on agar plates, incubate, and count colonies.
One colony represents one microbial cell.
Describe how to determine the rate of biocidal action on a given pathogen.
Determine initial viable count
Expose to the agent
Repeat viable counts
Calculate the decimal reduction time
Define decimal reduction time.
Time to reduce a population 10-fold at a particular temperature
Define sterility assurance.
The probability that a micro-organism could survive a sterilisation process
What is the relationship between the D-value and sterility assurance?
Descreasing linear
Define what is meant by biocidal. Is it reversible or irreversible?
Processes or agents that kill micro-organisms and are irreversible
Define what is meant by biostatic. Is it reversible or irreversible?
Processes or agents which inhibit microbial growth but are usually reversible.
Name 4 main methods used for sterilisation.
Heat
Filtration
Ionising radiation
Chemical agents
Differentiate between the effects of moist vs dry heat.
Moist heat coagulates
Dry heat oxidises
What is more effective, moist or dry heat? Describe why.
Moist heat is more effective.
When steam condenses, it liberates intense latent heat.
When would dry heat be used for sterilisation (6)?
Glass, metal, cutting instruments, powders, waxes, eye ointment bases
When would moist heat be used for sterilisation (2)?
Most non-heat sensitive instruments, decontamination of used articles
Name 4 advantages of dry heat.
Penetrates solids, usable on non-aqueous liquids, closed cavities, non-corrosive
Name 2 advantages of moist heat.
Rapid and effective
Name 3 disadvantages of dry heat.
Long times
Very high temperatures
Potentially very destructive
Name 2 disadvantages of moist heat.
Corrosive over time
Wets articles like wrappings
Briefly describe how an autoclave works.
Its like a pressure cooker.
Does filtration kill micro-organisms?
No, just removes them
By what two processes does filtration work?
A combination of adherence and exclusion
When are filters used?
For heat-sensitive liquids and air
Describe the structure of depth filters and what they are made of (3). Do they have good flow?
Maze-like fibrous sheet or mat
Can be made of paper, asbestos, or glass fibles
Has good flow
Describe the structure of membrane filters and what they are made of (2). Do they have good flow?
Large number of tiny holes like a sieve
Made of cellulose acetate or nitrate
Has good flow
Describe the structure of nucleation track filters and what they are made of. Do they have good flow?
Has a small number of holes like a mat
Made of very thin polycarbonate film, which is irradiated then etched
Has low flow rate
How does ionising radiation sterilise?
By creating free radicals which damage DNA
Name three advantages of using ionising radiation to sterilise.
Effective at ambient temperature
No wetting
Articles packaged ready for use
Name three disadvantages of using ionising radiation to sterilise.
High installation costs
Safety issues
Possible deleterious effects
Give two examples of sterilising chemicals.
Give an advantage and four disadvantages of these.
Gluteraldehyde and ethylene oxide
Advantage - broad spectrum
Disadvantage - slow, expensive, toxic residues, carcinogenic
Name three kinds of indicators for monitoring the effectiveness of sterilisation.
Physical
Chemical
Biological
Describe an example of a physical indicator for an autoclave.
A printer that contains the date, temperature, and time of sterilisation.
Describe an example of a chemical indicator for an autoclave.
An autoclave tape which changes colour at a given temperature
Describe an example of a biological indicator for an autoclave.
Spore strips which are placed into the autoclave as well and checked for viability
Briefly describe the hazard analysis critical control points process.
A way to make a process more effective by identifying certain critical points in the process and monitoring them
Name three disinfection methods.
Simple washing and cleaning
Hot water/steam for shorter times
Chemical disinfectants
What is the aim of handwashing?
To remove transient flora
Does handwashing eliminate resident flora?
No, it can only be reduced
When should hands be washed (2)?
Before and after seeing a patient.
Name 5 properties that an ideal handwash should have.
Broad spectrum
Non-irritant
Non-allergenic
Rapid action
Residual action
What kinds of micro-organisms are the most susceptible to disinfectants (2)?
Vegetative bacteria
Enveloped viruses (influenza/HIV)
What kinds of micro-organisms are moderately susceptible to disinfectants (2)?
Acid-fast bacteria
Non-enveloped viruses
What kinds of micro-organisms are the least susceptible to disinfectants (4)?
Fungal and bacterial spores
Protozoal cysts
Prions
Name two disinfectants with a broad spectrum.
Aldehydes and halogens
Give three examples of disinfecting agents with a limited spectra.
Alcohols
Phenols
Chlorhexidine
Name 5 factors that affect the efficiency of a disinfectant.
Concentration
Contact time
Temperature
pH
Presence of organic material
Name a disinfectant that is effective in all situations.
None
What is essential to disinfecting?
Thorough pre-cleaning
Give an example of a halogen disinfectant and whether or not it leaves a toxic residue.
Hypochlorous acid
Non-toxic residue
What concentration are halogens used to clean tonometers and gonio prisms?
0.4-0.5%
What is an alternative to chlorhexidine when broader spectrum is needed? Explain briefly how it works.
Iodophors
Iodine is trapped in micelles and dispersed in a liquid colloid
What is a disadvantage of iodophors?
Can cause contact dermatitis
what concentration of hydrogen peroxide should be used to clean tonometers and gonio prisms?
3%
Do alcohol water mixtures leave residual activity after evaporating?
No
Are alcohol water mixtures effective against spores and cysts?
No
What can prolonged exposure to alcohol water mixtures cause?
Drying
What percentage of alcohol should be used for cleaning tonometers and gonio prisms?
70-80%
What should be used on dirty surfaces?
Phenols
What disinfectant is unaffected by organic material?
Phenols
What is essential when using phenols?
Accurate dilution
Are phenols effective against spores and non-enveloped viruses?
No
What is chlorhexidine less effective against, gram positive or negative?
Negative
Is chlorhexidine effective against spores and non-enveloped viruses?
No
Does chlorhexidine leave residual or cumulative action?
Both
Is chlorhexidine non-toxic?
Yes
Is chlorhexidine non-irritant and non-allergenic?
Yes
What two things affect the activity of chlorhexidine?
Anions and soaps
What disinfecting agent is useful for gram-positive bacteria and non-enveloped viruses?
Quaternary ammonium compounds
What are quaternary ammonium compounds easily inactivated by?
Organic matter
