Physical Means of Controlling Microbial Growth Flashcards
(55 cards)
1
Q
- making area/object safe to handle by inactivating/reducing contaminants to an accceptable level
- general term
A
Decontamination
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
3
Q
- less lethal than sterilization
- eliminates all pathogens, but not necessarily all microbial forms (endospores)
A
Disinfection
4
Q
List
What factors impact the efficacy of disinfection?
4
A
- Nature & Number of cells
- Type & concentration of disinfectant
- Type & condition of surface to be disinfected
- Duration of exposure
5
Q
- reduce number of microorganisms to a safe hygienic level
- less effective than disinfection
- safe for food contact
A
Sanitization
6
Q
- using antiseptics to reduce/eliminate microorganisms in and on the body
A
Antisepsis
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
8
Q
List
Physical Methods of Growth Control
3
A
- Heat
- Radiation
- Filtration
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
10
Q
the minimum, optimum, and maximum temperatures
that determine the growth of a microorganism.
A
cardinal temperature of microorganisms
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
12
Q
What measurements can we use to determine the effectiveness of sterilization methods?
2
A
- Decimal reduction time (D)
- Thermal death time
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)
14
Q
- Time it takes to kill all cells with a given temperature
- Determines heat sensitivity of the microorganism
A
Thermal death time
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
16
Q
How do we categorize the methods of heat sterilization?
2
A
- Dry heat
- Moist heat
17
Q
Differentiate dry & moist heat methods
3
A
(Dry vs Moist)
- no water vs with water
- heating & penetration (slow vs fast)
- sterilize objects & glassware vs kills microorganisms faster (less D value)
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
19
Q
- Use of open flame
- sterilize objects (wire loops, forceps, glass slides)
- prevent cross-contamination between microbial samples.
A
Flame-sterilization
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
21
Q
- Uses combustion to destroy any organic material in a sample
- turns into ash
A
Incineration
22
Q
What PH laws prohibit incineration?
A
Philippine Clean Air Act of 1999
Ecological Solid Waste Management Act of 2000
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
# T/F
Boiling is an effective sterilization method.
F - disinfection method only
26
* 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
Autoclaving
27
What are the conditions when autoclaving?
121ºC, 15 psi, 15- 20 mins
28
How does an autoclave kill heat resistant structures?
1. Chamber has pressure
2. ↑ latent heat of vaporization of water
3. ↑ temp of steam in autoclave
4. RIP even heat-resistant structures
29
* 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
Pasteurization
30
Examples of Pasteurization
| (2)
What are the conditions for each?
**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
# Differentiate
Decimal reduction time (D) of endospores vs vegetative cells
* Endospores: 121ºC @ 4-5 mins
* Vegetative cells: 65ºC @ 0.1-0.5 minutes
32
# List
Food-related factors that may affect heat sensitivity of endospores
3
How does it impact endospores?
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
# 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.
longer, higher
34
# Disinfection/Sterilization
1. Flame sterilization
2. Hot air convection oven
3. Incineration
4. Boiling
5. Autoclaving
6. Flash Pasteurization
7. Ultra-High Temperature Pasteurization
1. S
2. S
3. S
4. D
5. S
6. D
7. S
35
Filtration is best for ____.
heat-sensitive liquids and gases
36
Examples of filtration
| Bonus: via what?
1. Air filtration via depth filters
2. Liquid filtration via membrane filters
3. Nucleopore filter
37
* fibrous sheets made of overlapping
paper or glass fibers that trap air particles
* Ex. High-efficiency particulate air (HEPA) filter [disinfection]
depth filter
38
when circulating air is decontaminated through depth filters
air filtration
39
* 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.
High-efficiency particulate air (HEPA) filter
40
Size of particles that HEPA filter removes
< 3μm, > 10μm
41
* 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.
membrane filters
42
How does a membrane filter work?
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
* Thin polycarbonate film
* irradiated and chemically etched to yield uniform holes
* often used to isolate specimens for observation under a scanning electron microscope.
Nucleopore filter
44
# Sterlization/Disinfection
1. Air filtration (HEPA filter)
2. Liquid filtration via membrane filters
1. D
2. S
45
Classifications of radiation
non-ionizing or ionizing
46
* 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
UV radiation
47
wavelengths that UV light uses
220 - 300 nm
48
* 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
Ionizing radiation
49
What is Grays (Gy)?
Lethal dose for humans?
* 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
# Sterlization/Disinfection
1. Non-Ionizing Radiation
2. Ionizing Radiation
1. D
2. S
51
Food Preservation Methods
| 2
1. Low temperatures
2. Dehydration
52
How do low temperatures preserve food? At what temperatures?
* 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
Kinds of dehydration
Drying
Freeze-drying (lyophilization)
54
How does drying preserve food?
* Absence of water inhibits enzymatic activities
* Drying and dessication remove water from food products → preventing microbial growth
* Ex.: Yeast, dried fruit, etc.
55
How does freeze-drying preserve food?
* 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
