M: Sterilization, Disinfection, Infection Control - Week 8 Flashcards
What do ‘aseptic technique’ and ‘infection control’ involve?
Aseptic technique: involves using procedures to minimise the transfer of microorganisms
Infection control: involves the prevention or minimisation of cross infections
How do cross infections spread? (3)
- patient to staff
- staff to patient
- patient to patient
How can infections be spread? (3)
- direct contact
- aerosol
- instrument/equipment
When may optometrists be exposed to blood, tears and mucous membranes? (5)
When:
- remove a foreign body
- assessing patients with ocular trauma, conjunctivitis or microbial keratitis
- carrying out lacrimal lovage
- expressing glands and cysts
- fitting contact lenses
List 8 communicable diseases that could potentially be passed from patient to optometrist:
- HIV/AIDS
- Hep B and C
- TB
- Measles, mumps, rubella, chicken pox
- infectious mononucleosis
- herpes, influenza
- Adebovirus 8
- CID
Define the following:
A) cleaning
B) disinfection
C) sterilisation
A: removal of contaminating matter to reduce burden of organic material
B: removing from an article some or all of its burden of pathogenic microorganisms
C: destruction or removal of all viable microorganisms, spores and other infectious agents from an article
Explain the 3 classifications found in the Spaulding classification system of equipment uses
- Critical: invasive devices that enter normally sterile tissue or enter the vascular system by intent or accident
2: device contacts but does not penetrate mucous membrane
3: Device only contacts intact skin
List 3 factors that influence decision making in regards to whether to sterilise or disinfect
- risk and cost/benefit analysis
- Common sense
- Lobby groups (susceptible hosts)
What do you need to ensure a sterilisation/disinfection process is efficient? (3)
- Appropriate agent
- Appropriate conditions
- Appropriate apparatus (to ensure effective contact between agent and microorganisms)
What information do you need to design a sterilisation/disinfection process? (3)
- initial contamination level
- rate of biocidal action of agent
- sterility assurance required
Explain the process of obtaining a ‘Viable Count’ (5)
- prepare dilutions of sample
- spread on agar plates
- incubate plates
- count colonies
- estimate microbial load (one colony = one bacterial cell)
What does the D value represent?
The amount of time required to kill 90% of the organisms in a sample (ie a 10-fold reduction)
Define sterility assurance
A calculated probability that a microorganism could survive a sterilisation process and thereby render a proportion of treated articles unsterile
Name the 4 main methods of sterilisation
- Heat
- Filtration
- Ionising radiation
- Use of chemicals
Which heat is more effective at sterilisation: moist or dry?
Moist heat
List one advantage and one disadvantage of sterilisation by heat
Adv: reliable, available, economical
Disadv: heat causes physical and chemical changes which denature major cell constituents such as proteins
Explain the difference between moist and dry heat sterilisation
Moist heat coagulates. Dry heat oxidises
When do you use dry heat vs moist heat for sterilisation?
Dry: glass, metal, cutting instruments, powders, waxes, eye ointment bases
Moist: most non-heat sensitive instruments and materials; decontamination of used articles
List 4 advantages of dry heat sterilisation
- penetration of solids
- use for non-aqueous liquids
- closed cavities
- non-corrosive
List 2 disadvantages of dry heat sterilisation
- long times (up to 4 hours)
- high temperatures: potentially destructive
List 2 advantages of moist heat sterilisation
- rapid (esp. pre-vacuum, steam sterilisers)
- effective
List 2 disadvantages of moist heat sterilisation
- corrosive over time
- wets articles (including wrapping)
Define biocidal vs biostatic
Biocidal processes or agents kill microorganisms and are irreversible
Biostatic processes and agents inhibit microbial growth and are usually reversible
How does filtration sterilise?
Microorganisms are removed (not killed) by a combination of adherence and exclusion — so filter maintenance is critical
When are filters used? (2)
- for heat sensitive liquids, to obtain pyrogens free liquids, air
- different filters have different pore sizes ranging from 0.3 to 10um down to 10nm that are selected to exclude bacteria, mycoplasma, and, viruses
Describe depth filter. What’s it made of ? And how is it’s flow?
Fibrous sheet or mat, like maze
Made of: paper, asbestos, or glass fibres
Good flow rate
Describe membrane filter. What’s it made of? How’s the flow?
Large number of tiny holes, like sieve
Made of cellulose acetate or nitrate
85% space so good flow
Describe nucleation filter. What’s it made of? How’s the flow rate?
Small number of holes, like mat
Made of very thin polycarbonate film, irradiated then etched
Low flow rate
How does ionising radiation sterilise? List 3 advantages and disadvantages
By creating free radicals which damage DNA
Adv: effective at ambient temp, no wetting, articles packaged ready for use
Disadv: Hugh install costs, safety issues, possible deleterious effects
What is the rate of biocidal action?
Involves calculating how many organisms survive the sterilisation process over time
(Or more accurately, how many organisms are killed over time)
Provide 3 reasons why we dont just sterilise for a very long time
- cost
- efficiency
- could cause damage to the article/equipment
What requires a higher sterility assurance? A bandaid or syringe?
Syringe
What happens to the sterilisation process if you don’t wash the item beforehand?
It starts at a higher initial contamination therefore takes longer to sterilise to the amount you want
List 4 advantages and 4 disadvantages of using chemicals in sterilisation.
Adv: are bactericidal, virucidal, fungicidal and sporicidal (kills spores)
Disadv: slow, expensive, toxic residues, and carcinogenic
