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Heat
- fast, reliable, inexpensive,
- no chemical contamination.
- Above maximum growth temperatures biological changes in organic molecules leads to cell death. Fatal dehydration
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Direct Flame
simple incineration
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Hot Air Oven
- radiating dry heat
- Useful for dry powders, oily material, glassware
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Boiling Water
- moist heat penetrates better than dry heat thus, lower temp and shorter exposure time can be used
- Denatures protein
- Not sterilization for viruses and spores
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Autoclave
- moist heat inform of pressurized steam
- Most dependable forsterilization
- Higher gas pressure =higher gas temp
- Heat is sterilizing agent NOT pressured. Requirements: 15 pounds per square inch, 121.5 degrees C,15 minutes
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Pasteurization
- not sterilization
- Reduces bacterial population of a liquid
- Spores not affected
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Inorganic Filters
porcelain or ground glass
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Organic Filters
organic material in filter attracts organic material of organism
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Membrane filter
- cellulose acetate or polycarbonate control pore size
- Example: Hepa filters remove microbes from air
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UV Light (radiation)
- Exposed cell’s DNA absorbs energy
- Adjacent Thymine bases link (thymine dimmers), can’t replicate past it
- Chromosome replication impaired
- Maintenance proteins not produced
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Xrays and Gamma Rays
- Pass through microbial molecules via loss of electrons
- Creates ions (ionizing radiation)
- Combine with proteins and nucleic acids
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Chemical Control
- Rarely achieve sterilization
- Goal: destroy pathogen on or in an object (disinfection)
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Disinfectant
agent used on lifeless object
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Antiseptic
- agent used on living object
- Usually bacteriocidal: kills microorganisms
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bacteriostatic
temporarily prevents multiplication
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Sepsis
contamination of an object or tissue by microorganisms
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Aseptic
object or tissue free of contaminating microorganisms
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Sanitize
reduce microbe population to “safe” level
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Degerm
remove microorganisms from surface (ie: wash hands)
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