M: Sterilization, Disinfection, Infection Control - Week 8 Flashcards

1
Q

What do ‘aseptic technique’ and ‘infection control’ involve?

A

Aseptic technique: involves using procedures to minimise the transfer of microorganisms

Infection control: involves the prevention or minimisation of cross infections

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2
Q

How do cross infections spread? (3)

A
  • patient to staff
  • staff to patient
  • patient to patient
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3
Q

How can infections be spread? (3)

A
  • direct contact
  • aerosol
  • instrument/equipment
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4
Q

When may optometrists be exposed to blood, tears and mucous membranes? (5)

A

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
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5
Q

List 8 communicable diseases that could potentially be passed from patient to optometrist:

A
  • HIV/AIDS
  • Hep B and C
  • TB
  • Measles, mumps, rubella, chicken pox
  • infectious mononucleosis
  • herpes, influenza
  • Adebovirus 8
  • CID
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6
Q

Define the following:
A) cleaning
B) disinfection
C) sterilisation

A

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

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7
Q

Explain the 3 classifications found in the Spaulding classification system of equipment uses

A
  1. 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
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8
Q

List 3 factors that influence decision making in regards to whether to sterilise or disinfect

A
  1. risk and cost/benefit analysis
  2. Common sense
  3. Lobby groups (susceptible hosts)
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9
Q

What do you need to ensure a sterilisation/disinfection process is efficient? (3)

A
  1. Appropriate agent
  2. Appropriate conditions
  3. Appropriate apparatus (to ensure effective contact between agent and microorganisms)
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10
Q

What information do you need to design a sterilisation/disinfection process? (3)

A
  • initial contamination level
  • rate of biocidal action of agent
  • sterility assurance required
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11
Q

Explain the process of obtaining a ‘Viable Count’ (5)

A
  • prepare dilutions of sample
  • spread on agar plates
  • incubate plates
  • count colonies
  • estimate microbial load (one colony = one bacterial cell)
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12
Q

What does the D value represent?

A

The amount of time required to kill 90% of the organisms in a sample (ie a 10-fold reduction)

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13
Q

Define sterility assurance

A

A calculated probability that a microorganism could survive a sterilisation process and thereby render a proportion of treated articles unsterile

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14
Q

Name the 4 main methods of sterilisation

A
  1. Heat
  2. Filtration
  3. Ionising radiation
  4. Use of chemicals
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15
Q

Which heat is more effective at sterilisation: moist or dry?

A

Moist heat

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16
Q

List one advantage and one disadvantage of sterilisation by heat

A

Adv: reliable, available, economical

Disadv: heat causes physical and chemical changes which denature major cell constituents such as proteins

17
Q

Explain the difference between moist and dry heat sterilisation

A

Moist heat coagulates. Dry heat oxidises

18
Q

When do you use dry heat vs moist heat for sterilisation?

A

Dry: glass, metal, cutting instruments, powders, waxes, eye ointment bases

Moist: most non-heat sensitive instruments and materials; decontamination of used articles

19
Q

List 4 advantages of dry heat sterilisation

A
  • penetration of solids
  • use for non-aqueous liquids
  • closed cavities
  • non-corrosive
20
Q

List 2 disadvantages of dry heat sterilisation

A
  • long times (up to 4 hours)

- high temperatures: potentially destructive

21
Q

List 2 advantages of moist heat sterilisation

A
  • rapid (esp. pre-vacuum, steam sterilisers)

- effective

22
Q

List 2 disadvantages of moist heat sterilisation

A
  • corrosive over time

- wets articles (including wrapping)

23
Q

Define biocidal vs biostatic

A

Biocidal processes or agents kill microorganisms and are irreversible

Biostatic processes and agents inhibit microbial growth and are usually reversible

24
Q

How does filtration sterilise?

A

Microorganisms are removed (not killed) by a combination of adherence and exclusion — so filter maintenance is critical

25
Q

When are filters used? (2)

A
  • 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
26
Q

Describe depth filter. What’s it made of ? And how is it’s flow?

A

Fibrous sheet or mat, like maze

Made of: paper, asbestos, or glass fibres

Good flow rate

27
Q

Describe membrane filter. What’s it made of? How’s the flow?

A

Large number of tiny holes, like sieve

Made of cellulose acetate or nitrate

85% space so good flow

28
Q

Describe nucleation filter. What’s it made of? How’s the flow rate?

A

Small number of holes, like mat

Made of very thin polycarbonate film, irradiated then etched

Low flow rate

29
Q

How does ionising radiation sterilise? List 3 advantages and disadvantages

A

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

30
Q

What is the rate of biocidal action?

A

Involves calculating how many organisms survive the sterilisation process over time

(Or more accurately, how many organisms are killed over time)

31
Q

Provide 3 reasons why we dont just sterilise for a very long time

A
  • cost
  • efficiency
  • could cause damage to the article/equipment
32
Q

What requires a higher sterility assurance? A bandaid or syringe?

A

Syringe

33
Q

What happens to the sterilisation process if you don’t wash the item beforehand?

A

It starts at a higher initial contamination therefore takes longer to sterilise to the amount you want

34
Q

List 4 advantages and 4 disadvantages of using chemicals in sterilisation.

A

Adv: are bactericidal, virucidal, fungicidal and sporicidal (kills spores)

Disadv: slow, expensive, toxic residues, and carcinogenic