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BI 234 > Final: Ch 9: Physical & Chemical Control > Flashcards

Final: Ch 9: Physical & Chemical Control Flashcards

1
Q

4 techniques for controlling microorganisms

A

sterilization
disinfection
decontamination (sanitization)
antisepsis

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2
Q

Sterilization

A

kill/remove all microorganisms (including endospores) in a material/object

ex. autoclave or chemical sterilants

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3
Q

Disinfection

A

remove vegetative bacteria (not endospores)

ex bleach, iodine, boiling

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4
Q

Decontamination (sanitization)

A

mechanical removal of microorganisms/other debris to reduce contamination to safe levels

ex. soaps, detergents

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5
Q

Antisepsis “degerming”

A

reduces the # of microbes on the human skin
decontamination on living tissues

ex. alcohol, surgical hand scrubs

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6
Q

Sepsis

A

the growth of microorganisms in the blood and other tissues

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7
Q

Antiseptics

A

chemical agents applied directly to exposed body surfaces to prevent vegetative pathogens

skin and mucous membranes, wounds, and surgical incisions

  • prepping skin before surgical incisions
  • swabbing an open sore
  • ordinary hand washing w/a germicidal soap
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8
Q

Chemicals can be used to kill or inhibit microbial growth (few chemicals achieve sterility)

A

chemical agents are used on living tissues (as antiseptics) and on inanimate objects (as disinfectants)

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9
Q

3 Major principles of microbial control

A
  1. a definitive proportion of the organisms die in a given time interval
    - not all microbes die immediately
  2. the fewer organisms present, the shorter the time needed to achieve sterility
  3. microbes differ in their susceptibility to antimicrobial agents
    - need to match antimicrobial agents appropriately
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10
Q

Effectiveness of control depends on (factors):

A

of microorganisms
target population (bacteria, fungi, spores, viruses)
temp
pH
concentration of agent
mode of action (what is it attacking?)
interfering agents (solvents, debris, saliva, blood, feces)

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11
Q

Microbial death

A

microbial death = when they are no longer reproducing (permanent loss of reproductive capability even under optimal conditions)
they can still be metabolizing and stuff but if they arent reproducing = dead

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12
Q

Targets to control microbial presence

A 
injure cell wall
injure cell membranes
interfere w/nucleic acid synthesis
interfere w/protein synthesis
interfere w/protein function
remove microbes
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13
Q

Target: Cell wall

A 
bacteria and fungi:
-block synthesis
-degrade cellular components
-destroy or reduce stability
Agent:
-chemical: penicillin, detergents, alcohols
-physical: heat and radiation
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14
Q

Target: cell membrane

A 
All microbes and enveloped viruses:
-bind and penetrate lipids
-lose selective permeability (leakage)
Agent:
-chemical: surfactants
-physical: heat and radiation
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15
Q

Target: nucleic acid synthesis

A 
irreversibly bind to DNA:
-stop transcription and translation
-cause mutations
Agent:
-chemical: formaldehyde 
-physical: heat and radiation
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16
Q

Target: protein synthesis

A 
Binds to ribosomes:
-stops translation
-prevents peptide bonds
Agents:
-chemical: chloramphenicol
-physical: heat and radiation
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17
Q

Target: protein function

A 
Block protein active sites
Prevent binding to substrate
Dentature protein
Agent:
-chemical: alcohols, acids, phenolics, metallic ions
-physical: heat and radiation
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18
Q

Physical control methods: temperature and radiation

A 
Temp
-moist heat
-dry heat
-cold
Radiation
-ionizing
-ultraviolet
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19
Q

Killing with heat: oxidize and denature

A

most common method of sterilization

modes of action:
-oxidize & denature

Effectiveness varies with: kinds of microbes, their number, intensity, length of exposure, pH, moisture, nature of product

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20
Q

Moist heat sterilization

A 
most common and efficient method
2 kinds:
-boiling
-steam sterilization (autoclave)
moist heat is much hotter than dry (100 degrees in Oregon feels much hotter than in Arizona)
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21
Q

Boiling

A

effective on glassware and instruments
kills fungi, protozoa, bacteria, viruses in 10-30 min
requires 3 separate boilings to kill endospores
Pros: can use at home
Cons: messy, time consuming, materials may require drying, endospores may require longer time

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22
Q

Steam sterilization (autoclaving)

A

uses: liquids, glassware, instruments, bandages, contaminated material
steam must reach all surfaces to be effective
most efficient and convenient
kills all microbes in 15-20 min
materials may need drying

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23
Q

Dry heat

A 
types:
-oven (hot air) sterilization
-flaming inoculating loops
-incineration/burning
Temp and time of exposure is greater than moist heat
24
Q

Ovens

A

heat at 160-170 c for 2 hrs
kills microbes and endospores by oxidation or denaturation
used on glassware and instruments
cant be used on liquid media, cloth, plastics or articles wrapped in paper

25
Q

Incineration

A 
destroys contaminated materials:
-blood soaked swabs, bandages
-contaminated materials and objects
-entire diseased animal carcasses
safe and effective
26
Q

Thermal death time (TDT)

A

shortest length of time required to kill all test microbes at a specified temp

27
Q

Thermal death point (TDP)

A

lowest temp required to kill all microbes in a sample in 10 minutes

28
Q

Radiation

A

movement of energy in waves thru space and materials
high frequency = greatest penetrability
-waves strike molecules and knock out electrons
-releases ions and creates free radicals in cells
-ions attach to proteins and nucleic acids, damage cell structures, cause cell death
kills microbes on surfaces and within materials
good for heat sensitive items

29
Q

UV radiation

A

moderate wavelengths = low penetrability
wont penetrate paper glass or skin
kills microbes on surfaces

cross links DNA, inhibits replication, not safe to use on skin, causes burns and cancer

uses: sterilizes surfaces in labs and operating rooms; also vaccines, serum, toxins, drinking water and waste water
germicidal lamp in hospitals, schools, food prep areas

30
Q

High energy Ionizing radiation

A

gamma rays, x rays, electron beams
gamma rays use to sterilize glassware, surgical instruments, sterile drapes
electron beams used to sterilize pharmaceuticals, disposable plastic syringes, surgical gloves, etc

31
Q

Mechanical control methods

A

filtration:

  • liquid
  • gas
32
Q

Filtration

A

the passage of liquids and gases thru screen-like material w/pore sizes small enough to retain microbes
removes microbes - doesnt kill or inhibit them

used to sterilize air and heat sensitive material
gases are forced thru under positive pressure
liquids are either forced thru under pressure or pulled thru under vacuum
fluids are collected in sterile vessels

33
Q

Uses of filtration

A

heat sensitive material

removes bacteria, but not viruses, from plasma

34
Q

Air filtration

A

used in operating rooms, burn units, laminar flow hoods in high security pathogen

use high efficiency particulate air (HEPA)

35
Q

Chemical Agents

A

Range from disinfectants and antiseptics to sterilants ad preservatives
Aqueous solutions
Tinctures

36
Q

Aqueous solutions (chemical agents)

A

chemicals dissolved in pure water as the solvent

37
Q

Tinctures (chemical agents)

A

chemicals dissolved in pure alcohol or water-alcohol mixtures

38
Q

Chemical agents: Principles of Effective distribution

A

pay attention to the properties and concentration of the disinfectant

consider: the presence of organic matter, degree of contact with microorganisms, and temp

39
Q

Chemical agents: Qualities that an ideal disinfectant should have

A 
antimicrobial activity
solubility
stability
lack of toxicity for humans and animals
minimum activity by extraneous material
activity at ordinary temps
ability to penetrate
material safety
availability and low cost
40
Q

Chemical agents: how do you know if a disinfectant works?

A

Test it!
serial dilution test
disk diffusion test

41
Q

Chemical agents: Serial-dilution test

A

calculates # of surviving microbes after 10 min in disinfectant solution
the MIC

42
Q

Minimum inhibitory concentration (MIC)

A

the concentration required to inhibit growth of a specific isolate in vitro under standardized conditions

determined by finding the lowest dilution w/out visible growth during serial dilution testing
will vary for individual isolates

43
Q

Chemical agents: Disk diffusion test

A

filter paper disk is soaked w/disinfectant/antibiotic and applied to inoculated plate
look for inhibited growth

44
Q

Chemical agents: Types of chemical control agents

A

Phenols
Phenolics
Halogens: Iodine, chlorine
Alcohols
Heavy Metals
Quaternary Ammonium Compounds (Quats): Zephiran, cepacol
Chemical food preservatives: sodium dioxide, sodium benzonate, sodium nitrate
Aldehydes
Gaseous Chemosterilizers: ethylene oxide
Peroxygens: hydrogen peroxide, benzoyl peroxide, peracetic acid

45
Q

Controlling microbes in the lab: Refrigeration & Freezing

A

Bacteriostatic: inhibits growth and toxin production

slow freezing kills many microbes, but not all

survivors multiply when returned to growth temps (toxins produced previously are not affected)

not a sterilant

46
Q

Controlling microbes in the lab: Desiccation

A 
at ambient temps
essentially bacteriostatic
-kills many microbes (species sensitive)
-used to prepare foods, meats
-not a reliable sterilant!! Does not kill endospores and protozoan cysts
47
Q

Controlling microbes in the lab: Lyophilization

A

slow freezing under vacuum

removes water w/out ice crystal formation in cells = avoids cell damage

used to store bacteria and viruses as POWDERS

lyophilized microbes can be rehydrated and grown in culture

48
Q

Controlling microbes in food: Microwave radiation

A

kills bacteria by heating

unreliable sterilant!!!

  • ovens have “cold spots”
  • materials must be rotated to achieve even temp distribution
  • wont kill Trichinella cysts

a new version for labs sterilizes media in 10 min

49
Q

Controlling microbes in food: Osmotic pressure

A

adding large amounts of salt or sugar to foods creates a hypertonic environment for bacteria - causes plasmolysis

pickling, smoking, and drying foods have been used for centuries to preserve

osmotic pressure is never a sterilizing technique!!!

50
Q

Controlling microbes in food: Pasteurization

A

Disinfection of beverages
stops fermentation

mild heat (71) used to kill pathogens and reduce microbe populations

prevents transmission of milk-borne diseases
need to maintain taste and appearance

51
Q

Controlling microbes in food: Gamma Rays

A

kills bacteria in food
eliminates insects
prevents premature sprouting of seeds
extends shelf life

used on poultry, pork, fresh fruits, white potatoes, spices

may discolor food and/or alter taste
animals fed irradiated feed lose weight
no demonstrated risk from residual radiation

52
Q

6 factors that affect the action of antimicrobial agents

A
  1. # of microbes
  2. target population
  3. temp pH
  4. concentration of agent
  5. mode of action
  6. interfering agents
53
Q

High decontamination

A

types of microbe killed: endospore

applications: medical devices

54
Q

Medium decontamination

A

types of microbe killed: fungal spores, viruses, resistant pathogens

applications: disinfect items that come into contact with mucous membranes, but are non invasive

55
Q

Low decontamination

A

types of microbes killed: vegetative bacteria, vegetative fungal cells, some viruses

applications: clean electrodes, straps and pieces of furniture that touch skin surfaces but not mucous membranes

BI 234 (16 decks)

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