Transcript SI PPT: Control of Microbial cell growth

Updated: 3/31/2017 3:19:12 PM
Microbial Control of
Growth
Supplemental instruction
Fall 2010
For Dr. Wright’s Bio 7/27 Class
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Designed by Pyeongsug Kim ©2010 [email protected]
Bactericidal
-Kill the bacteria
-eg. Disinfectant, sterilization…
-Biocides
: Kill the microbes: bacteria, funcgi, viruses
Bacteriostatic
-Prevent(inhibit) growth of the bacteria
or reduce the microbes
-but does not kill the bacteria
Removal or dilution of the antimicrobial can result
in a resurgence of bacterial growth
-eg. Handwashing with soap
food in refrigerator
Picture from http://emssolutionsinc.wordpress.com/2009/08/
Designed by Pyeongsug Kim, ©2010 www.science-i.com
__________
Sterilization
- Bateriocides
-Free of microbes
-Bacteria(including endospores), fungi, and viruses.
-Not for prion(protein)!
-Bio7/27 Lab. Hospital,…
-eg. filtration, using heat (flaming loop), certain certain
chemicals, or irradiation
*Biocides – Kill microbes
Biostatics – Prevent microbes
Disinfection
__________
- Bateriocides or germercides *Kill microbes
-Disinfectants(Chemicals)
-Toxic or non-toxic to skin
-Objects or skin
-Water treatment Facilities
-Bacteria(including endospores), fungi, and
viruses.
-eg. Antiseptics (for skin)
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__________
Antiseptics
-Bacteriostatic
-Chemicals (Disinfectants)
-Non-toxic to skin
-Surgery, handwashing
- Bio7/27Lab. Hospitals,…
__________
Pasteurization
-Bateriocides or Bacteriostatics
-Brief heat
-Food or objects
__________
Degerming
- Bacteriostatics
-Surface area including skin.
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http://z.about.com/d/thyroid/1/0/K/X/surge
ry-clipart.jpg
http://altmed.creighton.edu/MilkPasteurization/Page1.htm
Sanitization
__________
-Biostatics
-Objects
-Health standards; clean in appearance
*no specific level of control
Preservation
__________
-Biostatics
-ingredients or conditions(temp. pH, dry….)
-Food or products
-Delay spoilage
- Jam, Pickling food, Dry food…
__________
Decontamination
-Biostatics
-heat, disinfectants, washing
-safe to handle
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______________
Aseptic
technique
-The use of specific methods to exclude contaminating
microorganisms from an environment.
- Microbiology laboratory, medical procedure….etc
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What types of organisms or other things are resistant to
disinfectants?
Endospores, Mycobacterium(waxy cell wall), Naked viruses,
Protozoan cysts & oocysts, Pseudomonas
Endospores
__________
-Resistant forms
-Much harder to destroy than vegetative cells.
-may destroy EXTREME heat or chemicals
Mycobacterium
__________
-Waxy cell walls
-detected by acid fast stains
-Resistant to chemicals
-May be required strong toxic to destroy
-TB
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http://diverge.hunter.cuny.edu/~weigang/Images/04-21_sporulation_1.jpg
__________
Naked viruses
-Lack of a lipid envelop
-More resistant to disinfectants than enveloped
-Poliovirus.
-However, viruses are NOT organisms or microbes.
but, viruses are pathogens.
Pseudomonas
_____________
-can metabolize many chemicals
-Grow in disinfectants!
-Hospital-acquired infection (nosocomial)
*Prion are new concern in Hospital, but rare.
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D value
_________
- the amount of time required to kill 90%
of organisms. (Or 10% remained.)
*Assumption: death occurs at a constant rate
D-Value = 10 minutes
100,000,000 are present.
100,000,000 ----(10min)  10,000,000
10,000,000 ----(10min)  1,000,000
1,000,000 ----(10min) 
100,000
100,000 ----(10min) 
10,000
10,000 ----(10min) 
1,000
1,000 ----(10min) 
100
100 ----(10min) 
10
10 ----(10min) 
1
Therefore, it takes 80 minutes
(8D-values) to kill all.
Designed by Pyeongsug Kim, ©2009
How about…
D-Value = 7 minutes
234,123,000 are present.
 Looks complicated to you? But, very simple!
234,123,000 cells are killed, in other word, 2 cells are
remained.
234,123,000  One!
234,123,000  Two!
234,123,000  Three!
234,123,000  Four!
234,123,000  Five!
234,123,000  Six!
234,123,000  Seven!
234,123,000  Eight! Stop!
7 min.(D-value) X 8 = 56 minutes. Or 8D values
Believe it or not… It is the answer.
Designed by Pyeongsug Kim, ©2009
Autoclaving
-high temperature, high pressure, steam
(121oC)
(15 psi)
-can kill endospores; may destroyprions
-Chemical indicators
Turn black indicates if the objects are exposed heat.
-Biological indicators
Change color  growth of endospores.  Wrongfully work!
-Bacteriocidal
-surgical instruments, microbial media for culture
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Pasteurization
-reduces numbers of microbes to tolerable
levels (bacteriostatics)
-HTST(High-temperature-short-time) method
brief heat (72 oC )
-UHT(Ultra-high-temperature) method
-Ice cream, Milk or juices, rubber, cloth,…
-Anesthesia masks in hospitals
Picture from http://altmed.creighton.edu/MilkPasteurization/Page1.htm http://www.outtakes.com/work/taster.html
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Commercial canning process
-Industrial-sized autoclave
-designed to kill spore formers(C.botulinum)
but, destroy almost all organisms.
-12 D process (kill 1012 organisms)
-Bacteriocidal
Dry heat
-flaming, baking, hot air oven
-sterilize certain items
-less effective than wet heat
-oxidizes cell components;
denature proteins.
-Bacteriocidal
-Glass Petri dishes and glass pipets
powders, oils, and other anhydrous
materials
Picture from http://www.directindustry.com/prod/memmert/laboratory-oven-28305-257562.html
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Chemicals
-disrupt tissue
cell membrane, proteins, DNA
-Disinfectants
:chemicals kill microbes
-antiseptics
non-toxic to skin
eg. Alcohol (weakly bacteriocidal)
Picture from http://www.ahptechnology.com/products/disinfectants
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Filtration  can sterilize but do not kill microbes.
-membrane
-sterilizes heat-sensitive liquids (drinking water)
-HEPA (high-efficiency particular air)
air filtration- filters remove particles.
Hospitals
-Laminar flow hoods
:protect workers and materials from
contamination.
Laboratory
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Radiation
- can be used foods.
control E.coli (0157:H7), Salmonella in beef, poultry…
- surgical supplies, drugs, Petri dishes
- Not for skin
- Bacteriocides
- Endospores resistant to radiation
•Gamma radiation
- penetrating
- damage DNA and cell membrane
•UV radiation
- poor pemnetrating
not effective for solid surfaces and turbid liquids
- damage DNA
- air, dringking water, surfaces…
-Caution! in human tissue (skin and eyes)  skin cancers
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Preservatives
Food preservation
-nontoxic for food
-Benzoic, sorbic
acids lower pH; bread, cheese, juice
prevent growth  bacteriostatics
by altering cell membrane function and energy
transformation
-Nitrate
inhibit spore formers  bacteriostatics
prcessed meats, bacon, ham
but, potential carcinogens
-Preservation for non-food items
sampoo, deodorants, soaps, mouth wash….
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Cold storage
-low-temperature; freezing
-inhibit growth bacteriostatic
-enzymatic inactive
-Psychrophiles can grow
 spoil the food in refrigerator
Drying
-draw water out of cells; dehydration
-inhibit growth bacteriostatic
-Drying food
Desiccation (removing water)
Lyophilization(freeze-drying)
~ coffee, milk, meats, vegetables
-Adding salt, sugar
S.aureus can grow in high salt conditions
meat jerkies
Designed by Pyeongsug Kim, ©2010 www.science-i.com