Sterilization and disinfection (midterm) Flashcards
What is the decreasing order of resistance to killing agents?
Prions > spores > mycobacteria > nonlipid viruses > fungi > bacteria > lipid viruses
How long should betadine (povidone-iodine) be kept in contact with the object to be disinfected?
1–2 minutes
What is the procedure for sterilization by a hot air oven?
Exposing the item to 160–170ºC for 1–2 hours
What are the types of sterilization by moist heat?
Temperature below 100ºC
* Pasteurization
* Inspissation
Temperature at 100ºC
* Boiling
* Tyndallization
Temperature above 100ºC
* Autoclaving
What are the types of sterilization by dry heat?
- Red heat
- Flaming
- Incineration
- Hot air oven
What is the procedure of Pasteurization?
Use moist heat at either:
* 72ºC for 20 seconds, then rapid cooling (Flash method), or,
* 63ºC for 30 minutes (Holder method)
What is the procedure of inspissation?
Exposing the object to humidity at 75ºC for 2 hours, on three successive days
What is Pasteurization usually used for?
Inactivating harmful organisms in milk
What is inspissation usually used for?
Sterilizing media containing proteins, e.g. serum
What is the process of Tyndallization?
Exposure to steam for 20–30 minutes on three consecutive days
What is Tyndallization used for?
Sterilizing media which cannot withstand prolonged boiling (e.g. sugars and gelatin)
What is the process of autoclaving?
Exposure to saturated steam at 121ºC for 15–20 minutes
How is autoclaving monitored?
Chemical tests: autoclave tape, Browne’s tube
Biological tests: adding a spore-bearing organism and attempting to culture it later
What are the methods of irradiation?
- UV radiation
- IR radiation
- Ionizing radiation (gamma rays)
What is the property of high-level disinfectants?
Kill all microbial pathogens, except a small number of spores
