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8/6/2019 288-035 Isolation of Microorganisms
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Kenneth S. Destura, RMT
ISOLATION OF PURE CULTUREOF ORGANISM & INHIBITION
AND DESTRUCTION OF
MICROORGANISMS
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Isolation of PureCulture of Organism
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ISOLATION OF PURECULTURE
COLONIES
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SERIAL DILUTIONPOUR PLATE
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SERIAL DILUTIONPOUR PLATE
Nutrient Agar
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SERIAL DILUTIONPOUR PLATE
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SERIAL DILUTIONPOUR PLATE
Quebec ColonyCounter
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SERIAL DILUTIONPOUR PLATE
Formula:
Number of bacteria/mL = colony count x reciprocal of
dilution
Number of colonies/plate = Ave. no. of colonies in 5
squares x 62.5
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STREAK PLATE METHOD
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STREAK PLATE METHOD
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STREAK PLATE METHOD
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STREAK PLATE METHOD
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Inhibition & Destructionof Microorganisms
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Inhibition and Destruction ofMicroorganisms
Definitions
Sterilization process whereby all forms of microbiallife, including bacterial spores are killed
Disinfection process whereby pathogenicorganisms but not necessarily all microorganisms orspores are destroyed
Antiseptic disinfectants used on living tissues
Biocides also known as chemical sterilants, theseare chemicals used to destroy all life
Disinfectants chemical sterilants used for shorterperiods
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Inhibition and Destruction ofMicroorganisms
Definitions
Thermal death point lowest temperature at whichall organisms in a liquid suspension can be killed in
10 minutes Thermal death time minimal length of time in which
all bacteria in a liquid suspension will be killed at agiven temperature
-cide - a suffix indicating that the agent will kill thekind of organism in question (e.g. viricide)
-static - a suffix indicating that the agent will preventthe growth of the type of organism in question (e.g.,
bacteriostatic)
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Inhibition and Destruction ofMicroorganisms
Factors influencing antimicrobial activity:
the concentration and kind of a chemical agent used;
the intensity and nature of a physical agent used;
the length of exposure to the agent;
the temperature at which the agent is used;
the number of microorganisms present;
the organism itself; and the nature of the material bearing the microorganism.
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Physical Agents
Heat
Moist heat
Autoclave
Boiling
Tyndallization
Pasteurization
Inspissation
Dry heat Hot air Sterilization
Incineration
Radiation
Ionizing
Non-ionizing
Filtration
Freezing
Deep Freezing
Lyophilization Ultrasound vibrations
Lasers
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Chemical Agents
QUATERNARY AMMONIUM COMPOUNDS -cationic detergentsused as disinfectants for food utensils and small instruments, andbecause of low toxicity, as antiseptics for skin; act by disruptingbiological membranes and possibly by denaturing proteins.
ALDEHYDES -reactive molecules that can be used as chemicalsterilants; may irritate the skin; act by combining with proteins andinactivating them
STERILIZING GASES (e.g., ethylene oxide, betapropio-lactone) -
can be used to sterilize heat-sensitive materials such as plasticpetri dishes and disposable syringes; act by combining withproteins and inactivating them. Recently, vapor-phase hydrogenperoxide has been used to decontaminate biological safety cabinet
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