Micobiology > Chapter 13 - Controlling Microorganisms > Flashcards

Chapter 13 - Controlling Microorganisms Flashcards

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1
Q

What are the relative resistances of microbes?

A
  • Highest resistance
  • Moderate resistance
  • Least resistance
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2
Q

What are the terminology and methods of control?

A
  • Sterilization
  • Disinfection
  • Antiseptic
  • Sanitization
  • Degermation
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3
Q

What are three methods used to destroy microorganisms? (decontamination)

A

Physical, chemical, and mechanical methods

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4
Q

Microorganisms that are targeted usually cause:

A

Infection or spoilage

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5
Q

What are some examples of microorganisms that are capable of causing infection or spoilage that need to be destroyed?

A
  • Vegetative bacterial cells and endospores
  • Fungal hyphae and spores, yeast
  • Protozoan trophozoites and cysts
  • Worms
  • Viruses
  • Prions
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6
Q

Microbial death is hard to detect, microbes often reveal no conspicuous _____ _____ to begin with

A

Vital signs

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7
Q

Microbial death is permanent loss of ____________ capability, even under optimum growth conditions

A

Reproductive

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8
Q
  • Factors that affect death rate

The effectiveness of a particular agent is governed by several factors. What are these factors?

A
  • Number of microbes
  • Nature of microbes in the population
  • Temperature and pH of environment
  • Concentration or dosage of agent
  • Mode of action of the agent
  • Presence of solvents, organic matter, or inhibitors
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9
Q
  • Practical concerns in microbial control

Selection of method of control depends on what circumstances?

A
  • Does the application require sterilization?
  • Is the item to be reused?
  • Can the item withstand heat, pressure, radiation, or
    chemicals?
  • Is the method suitable?
  • Will the agent penetrate to the necessary extent?
  • Is the method cost - and labor - efficient and is it safe?
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10
Q

What are the cellular targets of physical and chemical agents?

A
  1. The cell wall
  2. The cell membrane
  3. Protein and nucleic acid synthesis
  4. Proteins
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11
Q

What are the methods of physical control?

A
  1. Heat
  2. Cold temperatures
  3. Desiccation
  4. Radiation
  5. Filtration
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12
Q

What are the two modes of action and relative effectiveness of heat?

A
  1. Moist heat

2. Dry heat

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13
Q

Lower temperatures and shorter exposure time; coagulation and denaturation of proteins

A

Moist heat

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14
Q

Moderate to high temperatures; dehydration, alters protein structure; incineration

A

Dry heat

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15
Q

Bacterial endospores most resistant - usually require temperatures above _______

A

Boiling

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16
Q

What are the thermal death measurements?

A
  • Thermal death time (TDT)

- Thermal death point (TDP)

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17
Q

Moist heat methods include what two things?

A
  • Steam under pressure - sterilization
  • Autoclave - 15 psi/121 degrees C/10-40 minutes
  • Steam must reach surface of item being sterilized
  • Item must not be heat or moisture sensitive
  • Mode of action - denaturation of proteins, destruction of membranes and DNA
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18
Q

Intermittent sterilization for substances that cannot withstand autoclaving

A

Tyndallization

  • Items exposed to free-flowing steam for 30-60 minutes, incubated for 23-24 hours and then subjected to steam again
  • Repeat cycle for 3 days
  • Used for some canned foods and laboratory media
  • Disinfectant
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19
Q

Boiling water at 100 degrees C for 30 minutes to destroy _______________ pathogens
- Disinfection

A

Non-spore-forming

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20
Q

Heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value

A

Pasteurization

  • 63-66 degrees C for 30 minutes (batch method)
  • 71.6 degrees C for 15 seconds (flash method)
  • Not sterilization
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21
Q

___ ____ using higher temperatures that moist heat

A

Dry heat

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22
Q

What are the two forms of dry heat?

A
  1. Incineration

2. Dry ovens

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23
Q

Flame or electric heating coil

24
Q

150-180 degrees C - coagulate proteins

25
What are the two forms of cold?
1. Microbiostatic 2. Refrigeration - Used to preserve food, media, and cultures
26
Slows the growth of microbes
Microbiostatic
27
0-15 degrees C and freezing <0 degrees C
Refrigeration
28
Gradual removal of water from cells, leads to _________ __________
Metabolic inhibition
29
Not effective microbial control - many cells retain ability to grow when water is ____________
Reintroduced
30
Freeze drying; preservation
Lyophilization
31
Deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA
Ionizing radiation
32
What are some examples of radiation?
- Gamma rays, X-rays, cathode rays - Cold (low temperature) sterilization - Used to sterilize medical supplies and food products
33
Little penetrating power - must be directly exposed
Nonionizing radiation | - UV light creates pyrimidine dimers, which interfere with replication
34
- Filtration Physical removal of microbes by passing a ___ or ______ through filter. Used to sterilize heat sensitive _______ and ___ in hospital isolation units and industrial clean rooms.
- Gas or liquid | - Liquids and air
35
What are chemical agents in microbial control?
- Disinfectants - Antiseptics - Sterilants - Degermers - Preservatives
36
What are some desirable qualities of chemicals?
- Rapid action in low concentration - Solubility in water or alcohol, stable - Broad spectrum, low toxicity - Penetrating - Noncorrosive and nonstaining - Affordable and readily available
37
What are the levels of chemical decontamination?
- High-level germicides - Intermediate-level - Low-level
38
What are factors that affect germicidal activity of chemicals?
- Nature of the material being treated - Degree of contamination - Time of exposure - Strength and chemical action of the germicide
39
What are the germicidal categories?
1. Halogens 2. Phenolics 3. Chlorhexidine 4. Alcohols 5. Hydrogen peroxide 6. Detergents and soaps 7. Heavy metals 8. Aldehydes 9. Gases 10. Dyes
40
What are the halogens?
1. Chlorine | 2. Iodine
41
Cl2, hypochlorites (chlorine bleach), chloramines
Chlorine
42
I2, iodophors (betadine)
Iodine
43
- Disrupt cell walls and membranes and precipitate proteins - Low to intermediate level - bactericidal, fungicidal, virucidal, not sporicidal - Lysol - Triclosan
Phenolics
44
Antibacterial additive to soaps
Triclosan
45
- A surfactant and protein denaturant with broad microbial properties - Low to intermediate level - Hibiclens, Hibitane - Used as skin degerming agents for preoperative scrubs, skin cleaning, and burns
Chlorhexidine
46
- Ethyl, isopropyl in solutions of 50-95% - Act as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi - Intermediate level
Alcohols
47
- Produce highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to O2 gas - toxic to anaerobes - Antiseptic at low concentrations; strong solutions are sporicidal
Hydrogen peroxide
48
- Glutaraldehyde and formaldehyde kill by alkylating protein and DNA - Glutaraldehyde in 2% solution (Cidex) used as sterilant for heat sensitive instruments - High level
Aldehydes
49
- Disinfectant, preservative, toxicity limits use - Formalin - 37% aqueous solution - Intermediate to high level
Formaldehyde
50
- Ethylene oxide, propylene oxide, chlorine dioxide - String alkylating agents - High level - Sterilize and disinfect plastics and prepackaged devices, foods
Gases and aerosols
51
What is filtration?
- Physical removal of microbes by passing a gas or liquid through filter - Used to sterilize heat sensitive liquids and air in hospital isolation units and industrial clean rooms
52
- Ethylene oxide, propylene oxide, and chlorine oxide - Strong alkylating agents - High level - Sterilize and disinfect plastics and prepackaged devices, foods
Gases and aerosols
53
- Quaternary ammonia compounds (quats) act as surfactants that alter membrane permeability of some bacteria and fungi - Very low level
Detergents and soaps
54
Mechanically remove soil and grease containing microbes
Soaps
55
- Solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins - Oligodynamic action (little power) - Low level - Merthiolate, silver nitrate, silver
Heavy metals
56
- Aniline dyes are very active against gram-positive species of bacteria and various fungi - Sometimes used for antisepsis and wound treatment - Low level, narrow spectrum of activity
Dyes as antimicrobial agents
57
- Low level of activity - Each are a narrow spectrum - Each effect something specific
Acids and Alkalis
Micobiology
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