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BIO 120.01 > Physical Means of Controlling Microbial Growth > Flashcards

Physical Means of Controlling Microbial Growth Flashcards

1
Q
  • making area/object safe to handle by inactivating/reducing contaminants to an accceptable level
  • general term
A

Decontamination

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2
Q
  • completely eliminates all viable microorganisms, including most resistant forms
  • probability of a microorganism surviving is < 1/1,000,000
  • you’re pretty sure wala lang bacteria
  • ex. autoclaving
A

Sterilization

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3
Q
  • less lethal than sterilization
  • eliminates all pathogens, but not necessarily all microbial forms (endospores)
A

Disinfection

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4
Q

List

What factors impact the efficacy of disinfection?

4

A
  1. Nature & Number of cells
  2. Type & concentration of disinfectant
  3. Type & condition of surface to be disinfected
  4. Duration of exposure
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5
Q
  • reduce number of microorganisms to a safe hygienic level
  • less effective than disinfection
  • safe for food contact
A

Sanitization

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6
Q
  • using antiseptics to reduce/eliminate microorganisms in and on the body
A

Antisepsis

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7
Q

chemical agent used on body surfaces to safely reduce microbial numbers

Bonus: Give an example

A

Antiseptic

Iodine in Betadine, antibacterial soap, hydrogen peroxide, rubbing alcoh

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8
Q

List

Physical Methods of Growth Control

3

A
  1. Heat
  2. Radiation
  3. Filtration
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9
Q
  • most accessible and widespread method of controlling microbial growth
  • has to take into account the nature of the
    microorganism, its sensitivity to heat, and the duration
    of the heat treatment.
A

Heat Sterilization

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10
Q

the minimum, optimum, and maximum temperatures
that determine the growth of a microorganism.

A

cardinal temperature of microorganisms

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11
Q

What happens to a microorganism when exposed to its minimum/optimum/maximum growth temperature?
Why does that happen?

A

Minimum

  • activities are essentially frozen bc lack of energy → growth stops

Optimum

  • fastest growth bc it’s the best thermal conditions for met activities

Maximum

  • microbial growth stops bc denatured enzymes can’t do activities
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12
Q

What measurements can we use to determine the effectiveness of sterilization methods?

2

A
  1. Decimal reduction time (D)
  2. Thermal death time
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13
Q
  • Amount of time it takes to reduce a bacterial population 10—fold
  • Dependent on duration and temperature
  • Use to determine how sterilization methods are effective at reducing microbial numbers
A

Decimal reduction time (D)

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14
Q
  • Time it takes to kill all cells with a given temperature
  • Determines heat sensitivity of the microorganism
A

Thermal death time

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15
Q

For heat sterilization, the relationship between decimal reduction time and temperature is ____, and as you can see it, is dependent on the ____ of the treatment and the ____ being used.

A

logarithmic, duration, temperature

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16
Q

How do we categorize the methods of heat sterilization?

2

A
  1. Dry heat
  2. Moist heat
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17
Q

Differentiate dry & moist heat methods

3

A

(Dry vs Moist)

  1. no water vs with water
  2. heating & penetration (slow vs fast)
  3. sterilize objects & glassware vs kills microorganisms faster (less D value)
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18
Q

List examples of dry heat.
What is used in each example?

3

A

Flame-sterilization
* Use of open flame

Hot air convection oven
* Use of conduction as hot air circulates and heats up the objects in the chamber.
* 70ºC for 1 hr, 160ºC for 2 hrs (↑ temp & ↑ durations)

Incineration
* Uses combustion to destroy any organic material in a sample → ash

all sterilization

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19
Q
  • Use of open flame
  • sterilize objects (wire loops, forceps, glass slides)
  • prevent cross-contamination between microbial samples.
A

Flame-sterilization

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20
Q
  • Use of conduction
  • hot air circulates and heats up the objects in the chamber.
  • 70ºC for 1 hr, 160ºC for 2 hrs
  • ↑ temp & ↑ durations
A

Hot air convection oven

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21
Q
  • Uses combustion to destroy any organic material in a sample
  • turns into ash
A

Incineration

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22
Q

What PH laws prohibit incineration?

A

Philippine Clean Air Act of 1999
Ecological Solid Waste Management Act of 2000

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23
Q

Moist heat examples
What do they use?

A

Boiling
* heats water to 100ºC

Autoclaving
* uses steam & pressure

Pasteurization
* uses milk & heat-sensitive liquids

24
Q
  • simple disinfection
  • heats water to 100ºC
  • kills most pathogenic organisms
  • but endospores (& other heat-resistant structures) survive
A

Boiling

25
Q

T/F

Boiling is an effective sterilization method.

A

F - disinfection method only

26
Q
  • Uses steam coupled with pressure to kill microorganisms, including endospores
  • Pressure within the chamber → ↑ latent heat of vaporization of water, → ↑ temp of steam in autoclave → kill even heat-resistant structures.
  • It is the temperature (and not the pressure) that kills
  • Conditions: 121ºC, 15 psi, 15- 20 mins
A

Autoclaving

27
Q

What are the conditions when autoclaving?

A

121ºC, 15 psi, 15- 20 mins

28
Q

How does an autoclave kill heat resistant structures?

A
  1. Chamber has pressure
  2. ↑ latent heat of vaporization of water
  3. ↑ temp of steam in autoclave
  4. RIP even heat-resistant structures
29
Q
  • Disinfection
  • Used for milk and heat sensitive liquids
  • only reduces microbial load
  • Does not kill all microorganisms
  • Increases shelf life of perishable liquids
  • Kills pathogenic bacteria
A

Pasteurization

30
Q

Examples of Pasteurization

(2)
What are the conditions for each?

A

Flash Pasteurization (disinfection)
* Controlled milk flow rate through a tube
* Heats milk at 71ºC for 15s then cooled
* most common method used to pasteurize milk

Ultra-high temperature (UHT) (sterilization)
* 74ºC → 140ºC → 74ºC in less than 5 seconds
* rapid heating sterilizes the milk, can be stored at room temp for 1-3 months

31
Q

Differentiate

Decimal reduction time (D) of endospores vs vegetative cells

A
  • Endospores: 121ºC @ 4-5 mins
  • Vegetative cells: 65ºC @ 0.1-0.5 minutes
32
Q

List

Food-related factors that may affect heat sensitivity of endospores

3
How does it impact endospores?

A
  1. Low acidic pH kills microorganisms faster
  2. High sugar, protein, or fat content decreases heat penetration → slower reduction times
  3. Salt concentration - species specific
33
Q

Fill in the blank

If dry heat is used, the endospores must be exposed for a [longer/shorter] period and a [lower/higher] temperature to successfully
eliminate them.

A

longer, higher

34
Q

Disinfection/Sterilization

  1. Flame sterilization
  2. Hot air convection oven
  3. Incineration
  4. Boiling
  5. Autoclaving
  6. Flash Pasteurization
  7. Ultra-High Temperature Pasteurization
A
  1. S
  2. S
  3. S
  4. D
  5. S
  6. D
  7. S
35
Q

Filtration is best for ____.

A

heat-sensitive liquids and gases

36
Q

Examples of filtration

Bonus: via what?

A
  1. Air filtration via depth filters
  2. Liquid filtration via membrane filters
  3. Nucleopore filter
37
Q
  • fibrous sheets made of overlapping
    paper or glass fibers that trap air particles
  • Ex. High-efficiency particulate air (HEPA) filter [disinfection]
A

depth filter

38
Q

when circulating air is decontaminated through depth filters

A

air filtration

39
Q
  • Removes particles 3μm < particle < 10μm
  • Disinfection: 99.9% efficiency, but does not ensure sterilization
  • Used in clean rooms: quarantine, biological safety laboratories
  • also used inside biosafety cabinets, to make sure air doesn’t contaminate the samples being worked on by researchers.
A

High-efficiency particulate air (HEPA) filter

40
Q

Size of particles that HEPA filter removes

A

< 3μm, > 10μm

41
Q
  • Used in liquid filtration (sterilization)
  • Made of high tensile-strength polymers w/ numerous microscopic pores
  • Used with a syringe and sterile collecting vessel; acts like a sieve to trap particles
  • Filters are attached to a syringe holding liquid to be sterilized. By pushing the liquid out of the syringe and into a sterile collecting vessel, the filter acts like a sieve that traps particles, leaving you with a sterile liquid in the collecting vessel.
A

membrane filters

42
Q

How does a membrane filter work?

A
  1. Filters are attached to a syringe holding liquid to be sterilized.
  2. Liquid is pushed out of the syringe and into a sterile collecting vessel
  3. Filter acts like a sieve that traps particles
  4. Result: sterile liquid in the collecting vessel.
43
Q
  • Thin polycarbonate film
  • irradiated and chemically etched to yield uniform holes
  • often used to isolate specimens for observation under a scanning electron microscope.
A

Nucleopore filter

44
Q

Sterlization/Disinfection

  1. Air filtration (HEPA filter)
  2. Liquid filtration via membrane filters
A
  1. D
  2. S
45
Q

Classifications of radiation

A

non-ionizing or ionizing

46
Q
  • Disinfection
  • 220-300nm wavelengths
  • Causes mutations in DNA that results to microbial death
  • May become ineffective because of activated repair mechanisms that fix their UV-damaged DNA.
  • Limited to disinfecting exposed surfaces only
A

UV radiation

47
Q

wavelengths that UV light uses

A

220 - 300 nm

48
Q
  • sterilization
  • X-rays and gamma rays
  • Produces highly reactive molecules that can destroy DNA, lipids, and proteins, leading to cell death
  • Used to sterilize medical equipment and food products in large industrial companies
A

Ionizing radiation

49
Q

What is Grays (Gy)?
Lethal dose for humans?

A
  • absorbed radiation dose per gram of tissue
  • Lethal dose for humans is 10Gy.
  • Endospores can resists up to 3,300Gy
  • The measure for the amount of radiation needed to kill an organism
50
Q

Sterlization/Disinfection

  1. Non-Ionizing Radiation
  2. Ionizing Radiation
A
  1. D
  2. S
51
Q

Food Preservation Methods

2

A
  1. Low temperatures
  2. Dehydration
52
Q

How do low temperatures preserve food? At what temperatures?

A
  • Prevents spoilage and preserves food by decreasing microbial growth rate
  • Decreases amount of energy available to enzymes
  • Does not kill the microorganism
  • Refrigeration (~5ºC) and freezing (~ -20ºC)
53
Q

Kinds of dehydration

A

Drying
Freeze-drying (lyophilization)

54
Q

How does drying preserve food?

A
  • Absence of water inhibits enzymatic activities
  • Drying and dessication remove water from food products → preventing microbial growth
  • Ex.: Yeast, dried fruit, etc.
55
Q

How does freeze-drying preserve food?

A
  • Water from frozen materials are drawn out in a vacuum
  • Produces High-quality products viable for years
  • Food sent into space as rations for astronauts

BIO 120.01 (12 decks)

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