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Microbial Growth Control is Needed in
•Daily life
•Hospitals
•Microbiology laboratories
•Food production industry
•Other industries
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Sterilization
Removal or destruction of all forms of microbial life
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Disinfection
Control directed at destroying harmful microorganisms. Destruction of vegetative pathogens on inert surface
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Antisepsis
Destruction of vegetative pathogens on living tissue
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Asepsis
Object or area is free of pathogens
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Degerming
Mechanical removal of most of the microbes in a limited area
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Sanitization
any cleansing technique that mechanically removes microbes
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Bacteriostasis
inhibition of growth and multiplication of bacteria
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Biocide/Germicide
kills microorganisms with exception of endospores
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Selection of an Antimicrobial Procedure
•Type of microbe – ‘tough bugs’
•Number of microbes present
- •Environmental conditions
- –Organic material present?
- –Temp & pH (warm disinfectant vs
- cold?)
•Potential risk of infection
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Relative susceptibilities of microbes to antimicrobial agents
Most resistant: Prions, endospores, mycobacteria
Most susceptible: Enveloped viruses, G+ bacteria, non-enveloped viruses
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Virus structure: Naked
Without a lipid envelope
•Protein capsid
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Virus structure: Enveloped
With a lipid envelope covering the outside of the virus
•Phospholipid envelope
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Microbial control
Moist heat: lower temperatures and shorter exposure time; coagulation and denaturation of proteins
•Boiling
•Autoclaving
•Commercial canning
•Pasteurization
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Boiling Water
- •Boiling at 100oC for 30 minutes to destroy
- non-spore-forming pathogens
•Disinfection
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Pasteurization
- •Pasteurization – heat is applied to kill potential
- agents of infection and spoilage without destroying the food flavor or value
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Dry Heat
- •Dry heat: uses higher temperature than
- moist heat
•Hot oven (hot-air sterilization)
•Direct flaming
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Filtration of liquids
•Filter size excludes microbes (≤0.22 mm)
•Used for heat-sensitive liquids
–Ex. Antibiotics, vitamins, amino-acids
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Filtration of Air
- •HEPA filters: high-efficiency particulate
- air filters (0.3 mm)
•Infection-control rooms or laboratories
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Ionizing radiation
Gamma rays
•Produces reactive molecules that damage DNA
•Hydroxyl radicals, superoxide
•Used for sterilization of plastic disposables, Petri dishes
•Used in food preservation
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Non-ionizing radiation
UV light
- •Little penetrating power - must be directly
- exposed
•Damages DNA
•“Germicidal lamps”
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Organic Acids
- controls fungi, and some bacterial growth
- in foods & cosmetics
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sodium benzoate
•found naturally in cranberries, prunes, apples, cinnamon, cloves
Benzoic acid - naturally occurring compound; totally safe and has no adverse health implications
Benzene - known carcinogen
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