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Block 6 - week 4 > Sterilization, disinfection and containment - Kozel > Flashcards

Sterilization, disinfection and containment - Kozel Flashcards

1
Q

Define sterilization.

A

Use of physical or chemical agent to destroy all microbial formes, including spores.

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2
Q

Define disinfection.

A

Use of physical or chemical agents todestroy most microbial forms, bacterial spores or other relatively resistant organisms may remain viable.

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3
Q

Define antisepsis.

A

Use of chemical agents on skin or other living tissue to inhibit or eliminate microbes, no sporicidal action is implied.

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4
Q

Define biocide.

A

A general term describing a chemical agent, usually with broad spectrum, that inactivates microbes.

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5
Q

What are the factors influencing disinfectant potency?

A
  1. Concentration - effective concentration varies with disinfectant. There is a general inverse correlation between concentration and time required to kill
  2. Time - usually more time is better.
  3. pH - can dramatically influence potency
  4. Temp.- killing rate doubles for every 10 degrees centigrade that temp increases.
  5. presence of extraneous materials - these can bind or inactivate the disinfectant.
  6. microorganism - significant differences between microbes.
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6
Q

What microbes are the most vulnerable to disinfectants?

A

Lipid enveloped viruses.

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7
Q

From least resistant to most, list microbes.

A
  1. prions
  2. coccidia
  3. mycobacteria
  4. cysts
  5. small, non-enveloped viruses
  6. trophozoites
  7. gram-neg bacteria
  8. fungi
  9. large non-enveloped viruses
  10. gram-pos bacteria
  11. lipid enveloped viruses
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8
Q

Name some types of antiseptics and disinfectants.

A
  1. ethylene oxide and aldehydes
  2. oxidizing agents
  3. halogens
  4. phenolic compounds
  5. quaternary ammonium compounds
  6. alcohols
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9
Q

What are some types of ethylene oxide and aldehyde disinfectants?

A
  1. Formaldehyde - environmental decontamination; used in gaseous form or dissolved in water.
  2. Glutaraldehyde - chemical sterilization of equipment.
  3. Ethylene oxide - gaseous sterilization of heat sensitive materials.
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10
Q

What is the mechanism of action of ethylene oxide and aldehyde disinfectants?

A

They alkylate and cross-link macromolecules like proteins, DNA or RNA.

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11
Q

What are some oxidizing agents used as disinfectants?

A
  1. Ozone - disinfection of air systems.
  2. Hydrogen peroxide - cleansing of wounds, disinfection of implants, prostheses, etc.
  3. Peracetic acid - chemical sterilant.
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12
Q

What is the mechanism of action of the oxidizing agent type of disinfectants?

A

They oxidize proteins and cause DNA breakage.

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13
Q

Name some halogen disinfectants.

A
  1. Iodine - used as skin disinfectant.

2. Chlorine - chemical decontamination.

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14
Q

What is the mechanism of action of halogen disinfectants?

A

They oxidize proteins.

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15
Q

Name some types of phenolic compound type disinfectants.

A
  1. Chlorhexidine - skin disinfection.

2. Triclosan - antibacterial soaps, inumerable other uses.

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16
Q

What is the mechanism of action of phenolic compound disinfectants?

A

They disrupt the lipid containing membranes and denature proteins.

17
Q

Name some quaternary ammonium compound type of disinfectants.

A
  1. Benzalkonium chloride like Lysol - skin disinfection and hard surface cleaning.
18
Q

What is the mechanism of action of quaternary ammonium compound disinfectants.

A

They act as a surfactant. Their amphoteric properties disrupt membranes.

19
Q

Name a type of alcohol disinfectant.

A
  1. Isopropyl alcohol (70%) - skin decontamination, disinfection of fomites. 100% alcohol is less effective at killing.
20
Q

What is the mechanism of action of alcohol?

A

It denatures proteins.

21
Q

What are some ways that bacteria resist antiseptics and disinfectants.

A
  1. intrinsic resistance due to microbe variability and also physiological adaptation such as biofilms.
  2. decreased uptake - silver compounds.
  3. Efflux of agent - seen with quaternary ammonium compounds and chlorhexidine.
  4. Inactivation of agent - seen with chlorhexidine, formaldehyde and mercurials.
22
Q

What is temperature required to kill most pathogenic bacteria?

A

60 degrees Celcius.

23
Q

What is the temperature required to kill vegetative forms of all bacteria and fungi?

A

80 degrees Celsius.

24
Q

What is the temperature required to kill spores of pathogens?

A

100 degrees celsius.

25
Q

What is the temperature required to kill all bacterial spores?

A

120 degrees celsius.

26
Q

Describe some methods of using heat to kill microbes.

A
  1. Pasteurization - 72°C
  2. Boiling - 100°C
  3. Autoclave - Steam under pressure (the heat kills not the pressure) - 120°C
  4. Dry heat - 180°C, very inefficient
  5. incineration
27
Q

Name 2 types of physical agents used to kill or remove microbes.

A
  1. Radiation

2. Filtration

28
Q

Describe radiation.

A
  1. UV irradiation like sunlight or UV lights. This is used to control airborne or surface contamination - can’t penetrate solids.
  2. Ionizing radiation like X-ray and gamma emitters. This is used for sterilization of small, heat-sensitive articles.
29
Q

Describe filtration.

A
  1. Filter sterilization of heat-labile liquids - no removal of viruses or other small forms like some toxins - these can fit through pores.
  2. HEPA filtration of air - effective and even works for viruses.
30
Q

Describe the biosafety levels.

A

There are 4 levels.

  1. BSL-1 - basic level of containment with no special primary or secondary barriers used for work with well-characterized agents not known to consistently cause disease in healthy adults.
  2. BSL-2 - used in labs whose work involves broad spectrum of indingenous moderate-risk agents such as Hep B and HIV. Risks are skin, ingestion or mucous membrane exposure.
  3. BSL-3 - used in labs whose work involves indigenous exotic agents with potential for aerosol transmission. All work is done in a biosafety cabinet or other physical containment device.
  4. BSL-4 - used in labs whose work involves dangerous and exotic agents that pose a high risk of aerosol-transmitted lab infections and life-threatening diseases. All work is done in specialized safety cabinets.
31
Q

Give some specific examples of how to sterilize in the lab or medical setting.

A
  1. packages of surgical dressings - autoclave w/dry cycle
  2. liquids containing live virus - fix w/bleach then autoclave
  3. thermometer used in peds clinic - alcohol
  4. glass flasks of bacterial culture media - autoclave
  5. plastic pipettes in plastic wrappers - ionizing radiation
  6. pathogen contaminated glassware - autoclave
32
Q

Give some specific examples of how to sterilize in the lab or medical setting.

A
  1. 200 mL of tissue culture media - filter sterilize
  2. biosafety hood to change HEPA filters - formaldehyde gas
  3. skin at site of lumbar puncture - Iodine
  4. skin at site of venipuncture - alcohol
  5. raw milk - pasterurize
  6. lab bench after routine use for bacterial culture - phenol based disinfectant

Block 6 - week 4 (9 decks)

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