Lecture 13 Flashcards
Define disinfect
spores are not killed, but pathogens should be eliminated
Define sterilize
spores are killed along with vegitative cells, viruses, fungi, and protists
How can drug cocktails be made more effective?
mix drugs with very different modes of action
What is the method of choice in controlling microorganisms? Why?
heat sterilization
easy to control
leaves no residue
organisms can’t develop resistance
What is a disadvantage to using heat sterilization?
heat labile compounds are destroyed
Name the 2 types of physical methods to control microorganisms which involve heat
dry heat
moist heat
Define dry heat sterilization
stays dry the whole time
OR
ends up dry at the end of sterilization
Which is a faster process:
dry heat or moist heat sterilization?
moist heat
because proteins are more stable in dry heat
Name 2 different types of dry heat sterilization
Incineration
hot air oven
What happens during incineration?
very rapid oxidation of all organic material (organism burns)
heat speciment between 700-1500 degrees C
Only (inorganic) minerals left over
What is incineration used for? Give an example
biological waste disposal
EX:
Mad cow disease; incineration is the only certain way to get rid of the prions
What are prions?
amino acids which have folded incorrectly
Can you autoclave to remove mad cow disease?
Not really
one could autoclave the animal at 132 degrees for an hour, but the size and thickness of the cow would be difficult to assure full penetration
What is the mode of action of incineration?
Oxidation
Addition of oxygen = more intense oxidation
Removal of hydrogen = less intense (Protein oxidation)
What are the guidelines for time and temp of a hot air oven as a form of sterilization?
160 degrees C for 2 hours
How is the penetration of a hot air oven?
it has poor penetration
What is the mode of action of a hot air oven?
dehydration- removal of water
protein oxidation- removal of hydrogen, mild
protein coagulation- protein falls out of solution and solidifies (the protein is destroyed) [for an example cook some eggs]
Is moist heat sterilization slow or fast?
very fast
Name 6 types of moist heat sterilization
boiling free flowing steam steam under pressure high volume autoclave pasteurization milk sterilization
How can the boiling temperature of water be increased?
adding salt (NaCl or sodium carbonate)
What does scrubbing do?
decreases load and washes off spores
describe some characteristics of boiling
disinfects after 15 minutes
will kill spores after 5-9 hours
Does boiling sterilize or disinfect?
disinfect
the time it takes to kill spores is too long to be considered a viable sterilization method
What is the advantage of using free flowing steam?
less water log
Does free flowing steam sterilize or disinfect?
disinfect
does steam under pressure sterilize or disinfect?
sterilize
Is steam under pressure more effective at killing microorganisms than a hot air oven?
yes
moist air at 121.5 degrees is more sterilizing than dry air at the same temperature
What is an example of a way to sterilize using steam under pressure?
an autoclave
What does pressure do that makes steam under pressure more effective than boiling?
the pressure raises the water temperature
Are prions destroyed in a high vacuum autoclave?
no
What is the goal of pasteurization?
destroying all pathogens while maintaining the most flavor of the sample
What is the difference between batch and flash pasteurization
Batch is done in large quantites. Temp is lower (62.9), time is longer (30 minutes)
Flash is done in smaller batches at a hotter temperature (71.6) for a shorter amount of time (15 seconds)
What does the batch method of pasteurization kill?
Coxiella burnetti (Q-fever) mycobacterium bovis (a form of TB)
What is milk sterilization?
heat the milk to 140 degrees for less than a second
gives the milk a very long shelf life even without refrigeration
What is the difference between milk sterilization and pasteurization?
Milk sterilization is done at higher temperatures (140 degrees) for less time (<1 second); does not taste good
Pasturization is done at a lower temperature for longer (time and temp vary by the method)
What is the mode of action for moist heat?
protein coagulation
