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CVSOH1 Bacteriology > Sterilisation > Flashcards

Sterilisation Flashcards

1
Q
  1. What is not killed by autoclaving?
A
  1. Spore forming bacteria
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2
Q
  1. What may need to be treated in a manner to kill, prevent or reduce bacteria?
A
  1. Skin and other tissues, surgical instruments, gowns, wound dressings, solutions for injection and syringes, contaminatedd clothing and boots, animal habitats e.g. kennels, stables, lab media and solutions.
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3
Q
  1. A balance between what must be struck for each combo of microbe and item/area to be contaminated?
  2. How do agents used for decontamination compare to ABX? – How can they be used for patients?
  3. Give example of agent that cannot be used on a patient but can be used to sterilise surfaces.
  4. How are bacteria becoming resistant to chemical disinfectants?
A
  1. Balance between effectiveness of the treatment agent being used against an infectious agent and its potential to cause damage to a patient or item under treatment.
  2. They have a lower therapeutic index. – may be too toxic to use in a patient, but suitable for use on the skin for example.
  3. Chlorine
  4. Some are producing efflux pumps which can remove disinfectants.
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4
Q
  1. Define sterilisation.
  2. Define disinfection.
  3. Define sanitisation.
A
  1. Destruction/removal of all living cells, viable spores, viruses, viroids (nucleic acid infectious for plants) and prions (proteins infectious for animals e.g. the agents of scrapie and BSE) from an inanimate object or habitat. Chemicals (sterilants) and physical means are available.
  2. Destruction/removal or inhibition of microorganisms capable of causing disease from an inanimate object. Some vegetative cells and bacterial spores will remain following disinfection. Chemicals (disinfectants) and physical means are available.
  3. The reduction of microbial population on an inanimate objects to levels considered safe by public health standards.
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5
Q
  1. Define pasteurisation
  2. Define antisepsis
  3. Define germicide
A
  1. Inactivation of human pathogens and non-pathogenic spoilage organisms from milk, beer, wine and other beverages. Most other vegetative cells will also be inactivated but spores will remain.
  2. Destruction/removal or inhibition of micro-organisms from living tissue to prevent infection and disease. The chemical (antiseptics) used are less toxic to tissue than disinfectants would be.
  3. A chemical able to kill microorganisms e.g. bactericides, fungicides, viricides (bacteriostatic, fungistatic – chemicals able to inhibit growth).
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6
Q

4 categories of antimicrobial agents used today.

A

Moist heat
Dry heat
Radiation
Filtration

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7
Q
  1. What does moist heat do?
  2. Give examples of moist heat methods.
A
  1. Degrades nucleic acids, denatures enzymes and other essential proteins, and possibly denatures cell membranes.
  2. Boiling/steaming, autoclaving, tyndallisation, pasteurisation
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8
Q

Boiling/steaming…
1. At what temperatures of water are many microbes and viruses killed at? – Timing of exposure?
2. Temperature and timing of exposure to ensure complete death of all vegetative bacteria and fungi, viruses and eukaryotic spore, and some bacterial spores.
3. Purpose of boiling/steaming?

A
  1. 50-70C for a few minutes
  2. 100C for 10 mins
  3. Disinfection of objects not harmed by water but NOT sterilisation – Prions and some bacterial spores can survive treatment, even if extended for several hours.
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9
Q
  1. How does the autoclave work?
  2. What lb/in squared provides a temperature of 121C in autoclave?
  3. What is the sufficient amount of time under autoclave conditions for destruction of all microorganisms and spores?
  4. What is carried out for the autoclaving of absorbent materials and what does this involve?
  5. What should be done with material suspected of prion contamination before autoclaving?
A
  1. Temperature reaches >100C by saturated steam under pressure.
  2. 15
  3. 15-20 mins.
  4. A “dry run” whereby the moisture is drawn out after the autoclaving cycle and before the machine is opened.
  5. Should be soaked in 1N NaOH for 1-2hrs but preferable overnight.
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10
Q

Principles of autoclaving.

A

Increase in atmospheric pressure causes water to boil at >100C. (5psi = 109C, 10psi = 115.5C, 15psi = 121.5C, 20psi = 126.5C, 40psi = 141.5C).
Boiling water used to fill autoclave chamber (metal cylinder) with saturated steam, displacing the air present (vacuums may also be used to help remove air and reduce time taken).
Chamber outlets then closed but saturated steam continues to enter, causing pressure and hence temp rise.
Required temp and pressure reached, autoclaving continued for specified time.
Steam must be able to circulate freely and penetrate items being treated to sterilise them.
This, do not overpack autoclave chamber, keep packs small, keep fluid volumes small (5L will require ~70 mins to ensure sterility), loosen bungs and lids.
Include indicators in every autoclave run to ensure necessary conditions are reached.

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11
Q

What items is tyndallisation used on?
Temperature and time and purpose of this?
Next?
Then?
Disadvantages of tyndallisation?

A

Certain heat-sensitive materials e.g. media containing serum, milk or egg.

90-100C for 30-60 mins to kill vegetative organisms.

Incubate at 37C overnight to enable any spores present to germinate.

Process repeated on each of two further days resulting in sterilisation.

Time intensive.

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12
Q
  1. Pasteurisation old method temp and time?
  2. Flash method temp and time?
  3. Purpose of milk pasteurisation?
A
  1. 63C for 30 mins.
  2. 72C for 15 seconds followed by rapid cooling.
  3. Removal of vegetative human pathogens e.g. agents of tuberculosis and brucellosis and spoilage organisms. Rapid cooling discourages growth of remaining vegetative thermophiles and spores. NOTE: NOT STERILISATION! SPORES WILL SURVIVE!
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13
Q

In measuring heat-killing efficiency associated with moist heat….
1. Define thermal death point
2. Define thermal death time
3. What is the F value?
4. What is the D value?
5. Which of these measurements is most widely accepted?

A
  1. Lowest temperature at which all organisms/spores in a suspension are killed in 10 mins.
  2. Shortest time needed to to kill all organisms/spores in a suspension at a specified temperature under defined conditions.
  3. Time in minutes at a specified temperature (usually 121C) needed to kill a population of cells/spores.
  4. Decimal reduction time i.e. time in mins required to kill 90% of the organisms/spores in a sample at a specified temperature.
  5. D value.
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14
Q
  1. What is the D value for clostridium botulinum spores in phosphate buffer?
  2. What is the D value for clostridium perfringens spores in culture medium?
  3. What is the D value for salmonella species in chicken meat?
A
  1. D121 = 0.204
  2. D90 = 3-5
  3. D60 = 0.39-0.4
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15
Q

What are the 2 types of dry heat treatment?

A

Hot air oven and incineration.

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16
Q
  1. Temperature and time of the hot air oven?
  2. Useful for what material types?
  3. What should be done to material suspected of prion before entering the hot air oven and during?
A
  1. 160-170C for 2-3hrs.
  2. Glassware, metal instruments, products which would be ruined by water e.g. waxes, powders, oils.
  3. Soaked in 1N NaOH for 1-2hrs but preferably overnight, dry heat treatment for 4hrs as an added precaution.
17
Q

In what cases can incineration be used?

A

When the contaminated object/material is disposable.
Also applied to the sterilisation of bacteriological loops for culture work in the lab.

18
Q

What are the types of irradiation treatment?

A

UV and ionising radiation.

19
Q
  1. Wavelength of UV?
  2. What can UV kill? – how?
  3. How is its use as a sterilising agent limited?
  4. What can it sterilise?
  5. Safety consideration?
A
  1. 260nm
  2. Many types of vegetative microorganism – absorbed by the DNA causing thymidine dimers which inhibit replication and function.
  3. Unable to penetrate glass, water, films of dirt etc.
  4. Air and exposed surfaces in a room e.g. operating theatre.
  5. UV lamps should never be used when people or animals are in the room.
20
Q
  1. What radiation type is ionising radiation?
  2. How does it compare to UV?
  3. What can it sterilise?
  4. Considerations for labile solutions such as drugs, hormones and enzymes?
  5. Is it used in veterinary hospitals?
A
  1. Gamma radiation.
  2. Shorter wavelength so higher energy, deeper penetration.
  3. Sutures, dressings, heat sensitive materials e.g. catheters, prostheses, disposable plastics e.g. syringes etc.
  4. Can be sterilised with gamma radiation but potency may be reduced.
  5. No, only in industry.
21
Q

Name the other type of sterilisation.

A

Filtration.

22
Q
  1. What is filtration used for?
  2. Give examples of filtration material.
  3. Variation in pore sizes of filters?
  4. Common practice?
  5. How does it work?
A
  1. Sterilisation of heat or radiation sensitive material such as injection solutions, antibiotic solutions, non-viscous culture media, pharmaceuticals.
  2. sintered glass, asbestos, cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene fluoride.
  3. 0.2-10m
  4. Use prefilter with a large pore size to clarify a solution prior to using a small pore size (0.2m) to sterilise, thus avoiding clogging up latter with organic material.
  5. Material is forced through filter under pressure or drawn through a vacuum. Sterilisation can occur even if the pore size is slightly larger than the organism due to the degree of absorption to the filter material in addition to the filter effect.
23
Q

Categories of principle types of chemical agents used in veterinary.

A

Phenolics
Alcohols
Halogens
Quaternary ammonium compounds
Aldehydes
Sterilising gases
Miscellaneous

24
Q

What would be included in the specific manufacturers guidelines for use of a chemical antimicrobial agent?

A

Concentration
Length of application
Optimum pH of water
Optimum temperature of water
Optimum hardness of water
Stability
Water solubility
Toxicity
Shortfalls in activity

25
Q
  1. What would some chemical antimicrobial agents be inactivated to some degree by? – Give examples.
  2. How can this inactivation be prevented?
A
  1. Presence of excess organic matter
    – Faeces
    – pus
    – blood
    – exudates
    – discharges
  2. Clean the object or site prior to treatment.
26
Q
  1. Examples of phenolics?
  2. Activity of phenolics?
  3. Uses of phenolics?
  4. Advantages of phenolics?
  5. Disadvantages of phenolics?
A
  1. Creosol, Lysol, Staphene.
  2. Disinfectants – protein coagulation and cell membrane disruption.
  3. Varies with product – Equipment, linen, excreta, instruments, floors/walls.
  4. Not inactivated by organic material.
    Residual effect on surfaces.
    Kill Mycobacterium tuberculosis.
  5. Skin irritation
    Objectionable odours
    Creosol inactive in hard water.
27
Q
  1. Examples of alcohols.
  2. Activity of alcohols.
  3. Uses of alcohols.
  4. Advantages of alcohols.
  5. Disadvantages of alcohols.
A
  1. Ethanol, Isopropanol (conc. 70-90%)
  2. Disinfectants/antiseptics – Protein coagulation and cell membrane disruption.
  3. Instruments and thermometers, skin prep, hands.
  4. Kill Mycobacterium tuberculosis.
    Flammable so good for flaming instruments.
  5. Skin drying.
    Inactivated by organic matter.
    Flammable (dangerous).
28
Q

Chlorine halogens…
1. Examples.
2. Activity.
3. Uses.
4. Advantages.
5. Disadvantages.

A
  1. Hypochlorites (bleavhes) e.g. chloros, Milton
  2. Disinfectants – oxidise free sulphydryl groups.
  3. Floors/walls, fabrics if non bleachable.
  4. Kill Mycobacterium tuberculosis
  5. Bleaching
    Corrosive
    Inactivated by organic matter.
29
Q

Iodophors (halogens)…
1. Examples.
2. Activity.
3. Uses.
4. Advantages.
5. Disadvantages.
6. Why would iodophors be selected over iodine?

A
  1. Betadine, Wescodyne
  2. Disinfectants/Antiseptics – oxidise cell constituents, iodinate proteins.
  3. Varies with product – presurgical skin prep, thermometers, utensils, rubber items, milking/dairy operations.
  4. Cleaning
    Residual effect on surfaces
    Fading colour indicates loss of activity
  5. Kill Mycobacterium tuberculosis but only as tinctures (in alcohol).
  6. Iodine stains and may cause skin damage and allergies., but iodophors are non-staining and less irritant.
30
Q

Quaternary ammonium compounds (cationic detergents)…
1. Examples
2. Activity
3. Uses
4. Advantages
5. Disadvantages

A
  1. Cetrimide (e.g. Cetavlon), benzalkonium chloride (e.g. Roccal).
  2. Disinfectants/antiseptics – disrupt membranes and denature proteins.
  3. Small instruments, rubber items, skin antiseptics, wound/burn cleansing, milking/dairy operations.
  4. Cleansing.
  5. Does not kill M. tuberculosis.
    Does not kill Pseudomonas aeruginosa.
    Inactivated by hard H2O.
    Inactivated by soap.
31
Q

Aldehydes…
1. Examples
2. Activity
3. Uses
4. Advantages
5. Disadvantages

A
  1. Formalin (formaldehyde), gluteraldehyde.
  2. Crosslink proteins, kill bacteria, spores and fungi.
  3. Boot/foot/hoof dips. Used as a feed additive in USA.
  4. Broad spectrum.
  5. Inactivated by organic material.
    Causes contact dermatitis.
32
Q

Ethylene oxide gas…
1. Examples
2. Activity
3. Uses
4. Advantages
5. Disadvantages

A
  1. Carboxide, Steroxide
  2. Sterilants/disinfectants – denature proteins by substitution of alkyl groups with hydrogen atoms.
  3. Plastics, sutures, catheters, medical machine components, linen, rubber items, paper, lensed instruments.
  4. Rapid penetration of packing material (incl. plastic wraps).
  5. Special equipment needed (resembles an autoclave).
    Residual EO must be removed by aeration due to high toxicity.
33
Q
  1. How is the activity of chlorhexidine increased? – What are these products used for?
  2. How is chlorhexidine bactericidal?
A
  1. By being combined with a quaternary ammonium compound. – Presurgical scrub, obstetric procedures, milking/ dairy operations.
  2. Damages bacterial cell membranes and causes gelation of the cytoplasm of bacteria.
34
Q
  1. In what forms does anionic detergent come?
  2. Use?
  3. What are they combined with and why?
A
  1. Bars and liquids.
  2. Removing superficial bacteria from skin, floors, walls, utensils.
  3. Phenolics – to increase their bactericidal activity.
35
Q
  1. What is NaOH used for?
  2. What is 3% hydrogen peroxide used for?
  3. What heavy metal ions used to be used as germicides?
  4. What have these been replaced by? – why? – uses?
  5. What are still in use as antiseptics?
A
  1. Disinfection of stables/premises/transport.
  2. Wound disinfectant and cleanser, mouth wash for stomatitis.
  3. Mercury, arsenic, zinc, copper.
  4. Ionic and colloidal silver – less toxic and more effective. – Use against skin infections and antibiotic-resistant bacteria.
  5. Dilute solutions of silver nitrate and mercuric chloride.

CVSOH1 Bacteriology (2 decks)

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