Chapter 5: Control of Microbial Growth - Filtration, Temp, Pressure, etc. Flashcards
What is filtration? (2)
- vacuum used to force liquid through a filter with very small pores
- pores are too small for bacteria to pass
What are the sizes of the pores used in filtration?
- 0.1 μm, 0.22 μm or 0.45 μm
What type of liquids is filtration used to sterilize? Give some examples (4)
- temperature sensitive liquids
- antibiotics
- enzymes
- some vaccines
What filters are used in Air filtration?
- High-efficiency particulate air (HEPA) filters
Why do operating rooms use air filtration?
- to remove all microbes larger than 0.3 μm
What are two low temperature ways to control microbial growth?
- refrigeration and freezing
What does refrigeration do to microbes?
- slows or stops microbial growth
- bacteriostatic (or germistatic)
What does freezing do to microbes? (3)
- stops microbial growth
- only a small portion of microbes die
- bacteriostatic
What does high pressure do to microbes in liquid suspensions? (2)
- may kill bacterial cells (bactericidal)
- does not kill endospores
High pressure ___ is/is not sterilization.
is not
What is desiccation?
- removal of water (drying)
Does desiccation kill microbes? (3)
- slows or stops growth
- usually does not kill microbes
- bacteriostatic
What is osmotic pressure? (2)
- high concentrations of salts and sugars
- hypertonic environment
Does osmotic pressure kill microbes? (3)
- can kill some bacteria
- can be bactericidal or bacteriostatic
- molds and yeasts are more resistant
What microbes does radiation kill?
- DNA
- you would usually use radiation after the other techniques to kill DNA
What occurs in radiation? (2)
- X-rays and Gamma rays penetrate materials
- UV and high energy electron beams used on surfaces
How are microwaves used to kill microorganisms? (3)
- do not kill microorganisms directly
- they heat water
- then high temps can be used to disinfect materials
In lecture, why does heating a towel to sterilize it not work?
- some ppl wet a kitchen towel and put it in the microwave to remove smell
- not effective since water must be heated FIRST before the microwave can kill the microbes
