Physical ways to remove microorganisms

Sterilization

Removal of all microbial life

Commercial sterilization

Removal of endospores + microbial life

• canned food, etc

Disinfection

Removal of growing, vegetating pathogens from inanimate objects by chemical means

Antisepsis

Removal of pathogens from living tissue

• like disinfection

Sanitization

To lower microbial counts to a safe enough level for public health

• cleaning a public bathroom or restaurant silverware

Sepsis

Microbial contamination

Asepsis

The absence of significant contamination

Degerming

Removal of microbes from a limited area

• from skin using soap and water

• the skin around where a needle will go

Thermal death point (TDP)

lowest temperature at which all cells in a culture are killed in 10 mins

Thermal death time (TDT)

time to kill all cells in a culture

Decimal reduction time (DRT)

minutes to kill 90% of a population at a given temperature

Moist heat

• denatures proteins

• most effective

Dry heat sterilization:

• kills by oxidation

• needs to be really hot (incineration, flaming, hot-air sterilization)

• less effective

Autoclave (type of moist heat)

Steam under pressure

• goes above boiling point

• kills vegetative cells and endospores in about 15 minutes

• drawbacks: kills other molecules too

Pasteurization

Reduces spoilage organisms and pathogens by heating at a low temp for a longer time

• used for things that cannot withstand high temp and pressure

Equivalent treatments to pasteurization

• 63 degrees C for 30 minutes

• high-temp short-time (HTST) 72 degrees C for 15 seconds

• ultra-high-temp (UHT) 140 degrees C for less than 1 second

Refrigerating + Freezing

Inhibit microbial growth

• bacteriostatic

Surfactants: Soap

Degerming

• breaks bonds that hold molecules together/on our skin, allowing them to be washed off

Surfactants: Acid-anionic detergents

More effective than soap at breaking surface tension/disrupting microbial interactions

• negative charge/anionic

Surfactants: Quaternary ammonium compounds

Bactericidal because they change membrane permeability allowing loss of ions (like potassium) and more to leak out of the cell.

• positively charged/catatonic