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

Final: Ch 9: Physical & Chemical Control Flashcards

(55 cards)

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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

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

Ovens

Study These Flashcards
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
Incineration
``` destroys contaminated materials: -blood soaked swabs, bandages -contaminated materials and objects -entire diseased animal carcasses safe and effective ```
26
Thermal death time (TDT)
shortest length of time required to kill all test microbes at a specified temp
27
Thermal death point (TDP)
lowest temp required to kill all microbes in a sample in 10 minutes
28
Radiation
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
UV radiation
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
High energy Ionizing radiation
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
Mechanical control methods
filtration: - liquid - gas
32
Filtration
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
Uses of filtration
heat sensitive material | removes bacteria, but not viruses, from plasma
34
Air filtration
used in operating rooms, burn units, laminar flow hoods in high security pathogen use high efficiency particulate air (HEPA)
35
Chemical Agents
Range from disinfectants and antiseptics to sterilants ad preservatives Aqueous solutions Tinctures
36
Aqueous solutions (chemical agents)
chemicals dissolved in pure water as the solvent
37
Tinctures (chemical agents)
chemicals dissolved in pure alcohol or water-alcohol mixtures
38
Chemical agents: Principles of Effective distribution
pay attention to the properties and concentration of the disinfectant consider: the presence of organic matter, degree of contact with microorganisms, and temp
39
Chemical agents: Qualities that an ideal disinfectant should have
``` 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
Chemical agents: how do you know if a disinfectant works?
Test it! serial dilution test disk diffusion test
41
Chemical agents: Serial-dilution test
calculates # of surviving microbes after 10 min in disinfectant solution the MIC
42
Minimum inhibitory concentration (MIC)
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
Chemical agents: Disk diffusion test
filter paper disk is soaked w/disinfectant/antibiotic and applied to inoculated plate look for inhibited growth
44
Chemical agents: Types of chemical control agents
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
Controlling microbes in the lab: Refrigeration & Freezing
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
Controlling microbes in the lab: Desiccation
``` 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
Controlling microbes in the lab: Lyophilization
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
Controlling microbes in food: Microwave radiation
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
Controlling microbes in food: Osmotic pressure
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
Controlling microbes in food: Pasteurization
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
Controlling microbes in food: Gamma Rays
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
6 factors that affect the action of antimicrobial agents
1. # of microbes 2. target population 3. temp pH 4. concentration of agent 5. mode of action 6. interfering agents
53
High decontamination
types of microbe killed: endospore | applications: medical devices
54
Medium decontamination
types of microbe killed: fungal spores, viruses, resistant pathogens applications: disinfect items that come into contact with mucous membranes, but are non invasive
55
Low decontamination
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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