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Micobiology > Chapter 13 - Controlling Microorganisms > Flashcards

Chapter 13 - Controlling Microorganisms Flashcards

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

A

Incineration

24
Q

150-180 degrees C - coagulate proteins

A

Dry ovens

25
Q

What are the two forms of cold?

A
  1. Microbiostatic
  2. Refrigeration
    - Used to preserve food, media, and cultures
26
Q

Slows the growth of microbes

A

Microbiostatic

27
Q

0-15 degrees C and freezing <0 degrees C

A

Refrigeration

28
Q

Gradual removal of water from cells, leads to _________ __________

A

Metabolic inhibition

29
Q

Not effective microbial control - many cells retain ability to grow when water is ____________

A

Reintroduced

30
Q

Freeze drying; preservation

A

Lyophilization

31
Q

Deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA

A

Ionizing radiation

32
Q

What are some examples of radiation?

A
  • Gamma rays, X-rays, cathode rays
    • Cold (low temperature) sterilization
    • Used to sterilize medical supplies and food products
33
Q

Little penetrating power - must be directly exposed

A

Nonionizing radiation

- UV light creates pyrimidine dimers, which interfere with replication

34
Q
  • 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.
A
  • Gas or liquid

- Liquids and air

35
Q

What are chemical agents in microbial control?

A
  • Disinfectants
  • Antiseptics
  • Sterilants
  • Degermers
  • Preservatives
36
Q

What are some desirable qualities of chemicals?

A
  • Rapid action in low concentration
  • Solubility in water or alcohol, stable
  • Broad spectrum, low toxicity
  • Penetrating
  • Noncorrosive and nonstaining
  • Affordable and readily available
37
Q

What are the levels of chemical decontamination?

A
  • High-level germicides
  • Intermediate-level
  • Low-level
38
Q

What are factors that affect germicidal activity of chemicals?

A
  • Nature of the material being treated
  • Degree of contamination
  • Time of exposure
  • Strength and chemical action of the germicide
39
Q

What are the germicidal categories?

A
  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
Q

What are the halogens?

A
  1. Chlorine

2. Iodine

41
Q

Cl2, hypochlorites (chlorine bleach), chloramines

A

Chlorine

42
Q

I2, iodophors (betadine)

A

Iodine

43
Q
  • Disrupt cell walls and membranes and precipitate proteins
  • Low to intermediate level - bactericidal, fungicidal, virucidal, not sporicidal
    - Lysol
    - Triclosan
A

Phenolics

44
Q

Antibacterial additive to soaps

A

Triclosan

45
Q
  • 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
A

Chlorhexidine

46
Q
  • Ethyl, isopropyl in solutions of 50-95%
  • Act as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi
  • Intermediate level
A

Alcohols

47
Q
  • 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
A

Hydrogen peroxide

48
Q
  • Glutaraldehyde and formaldehyde kill by alkylating protein and DNA
  • Glutaraldehyde in 2% solution (Cidex) used as sterilant for heat sensitive instruments
  • High level
A

Aldehydes

49
Q
  • Disinfectant, preservative, toxicity limits use
  • Formalin - 37% aqueous solution
  • Intermediate to high level
A

Formaldehyde

50
Q
  • Ethylene oxide, propylene oxide, chlorine dioxide
  • String alkylating agents
  • High level
  • Sterilize and disinfect plastics and prepackaged devices, foods
A

Gases and aerosols

51
Q

What is filtration?

A
  • 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
Q
  • Ethylene oxide, propylene oxide, and chlorine oxide
  • Strong alkylating agents
  • High level
  • Sterilize and disinfect plastics and prepackaged devices, foods
A

Gases and aerosols

53
Q
  • Quaternary ammonia compounds (quats) act as surfactants that alter membrane permeability of some bacteria and fungi
  • Very low level
A

Detergents and soaps

54
Q

Mechanically remove soil and grease containing microbes

A

Soaps

55
Q
  • Solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins
  • Oligodynamic action (little power)
  • Low level
  • Merthiolate, silver nitrate, silver
A

Heavy metals

56
Q
  • 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
A

Dyes as antimicrobial agents

57
Q
  • Low level of activity
  • Each are a narrow spectrum
  • Each effect something specific
A

Acids and Alkalis

Micobiology (15 decks)

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