CONTROL OF MICROBIAL GROWTH

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CONTROL OF MICROBIAL GROWTH Asepsis - keep
pathogens out (without infection) Antisepsis
prevent infection or sepsis Sterilization - kill
all organisms Disinfection - reduce
pathogens Antiseptic - agent to kill pathogens
on skin Disinfectant - reduce/kill pathogens on
surfaces Bactericidal kill bacteria Bacteriost
asis - inhibit bacterial growth Sanitization -
reduce pathogens on surfaces to safe levels
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Microbial death exponential or logarithmic
function number reduced by same fraction at a
constant interval log vs. exposure time is
linear
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Microbial death exponential or logarithmic
function number reduced by same fraction at a
constant interval log vs. exposure time is
linear Conditions affecting agent
effectiveness population size death rate is a
log function population composition concentratio
n or intensity of agent conc for chemical,
intensity for physical duration of
exposure temperature local environment (pH,
organic matter)
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PHYSICAL CONTROL METHODS Temperature - moist
heat, dry heat Boiling - 10 min for cells, hours
for spores Autoclave - 10-15 min for spores
121ºC and 15 lb pressure nutrients
preserved Pasteurization - 63ºC for 30 min
72ºC for 15 sec 140ºC for 3 sec Dry heat
- 160-180ºC for 2-3 hr Refrigeration Freezing
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Pasteurization
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PHYSICAL CONTROL METHODS Temperature - moist
heat, dry heat Boiling - 10 min for cells, hours
for spores Autoclave - 10-15 min for spores
121ºC and 15 lb pressure nutrients
preserved Pasteurization - 63ºC for 30 min
72ºC for 15 sec 140ºC for 3 sec Dry heat
- 160-180ºC for 2-3 hr Refrigeration Freezing
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PHYSICAL CONTROL METHODS Filtration Desiccation
Radiation x-rays - artificially
generated gamma rays - radioactive decay UV
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PHYSICAL CONTROL METHODS Radiation visible
light??
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PHYSICAL CONTROL METHODS Radiation visible
light??
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CHEMICAL CONTROL METHODS Ideal
agent Effective against many types of
organisms Effective at low concentration Non-t
oxic to humans Stable Cheap Selecting an
agent What organism? What object?
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CHEMICAL CONTROL METHODS Antiseptics
Disinfectants Phenol related
compounds Phenol coefficient Chlorhexidine Ha
logens I2 iodophor Cl2 hypochlorite Tincture
of iodine Alcohols 70 Heavy metals -
silver, mercury Surfactants detergents
quarternary nitrogen compounds
dilution killing in 10 min, not 5____
dilution phenol killing in 10 min, not 5
Phenol coefficient
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CHEMICAL CONTROL METHODS Antiseptics
Disinfectants Phenol related
compounds Phenol coefficient Chlorhexidine Ha
logens I2 iodophor Cl2 hypochlorite Tinctu
re of iodine Alcohols 70 Heavy metals -
silver, mercury Surfactants detergents
quarternary nitrogen compounds