Using heat to kill Microbes

How does heat kill microbes? (1)

• Destroys enzymes (stops chemical reactions keeping cell alive)

Boiling for 5 minutes kills: (2)

• most pathogenic bacteria (not all endospores)

• most viruses

is boiling disinfection or sterlization?

disinfection, (does not kill or remove everything)

What is pasteurization? (1)

Killing pathogens and microbes to slow spoilage (eg. stop fermentation)

What is classic treatment pasteurization? (1)

mild heating to 63 C for 30 minutes

What is HTST (High Temp Short Time) for pasteurization? (1)

72 C for 15 seconds

What is UHT (ultra high temperature) and what seperates it from the other pasteurizations? (2)

• 140 C for 3 seconds

• Its sterilization for microbes growing in normal conditions

What does an autoclave do?

Uses 15 psi of pressure and 121 C of steam to sterilize

What do autoclaves kill in about 15 mins? (1)

Endospores (15 mins of those conditions)

What are autoclaves considered the best method for? (1)

Sterilization

What are autoclaves used for? (3)

• Culture media (eg. flask)

• Hospital instruments

• Hospital materials that can withstand heat and moisture

What is required of all solid surfaces to be sterilized by the autoclave? (1)

They must be exposed to the steam

What is required of all liquids to be sterilized by the autoclave? (1)

They must reach a temperature of 121 C

What is direct flaming? (1)

Sterilizing inoculation needles by holding it over a flame until it turns red hot (or white hot for eg. platinum)

What is Incineration? (1)

A way to get rid of contaminated materials (burnt to a crisp)

What does hot air Sterilization use? (1)

A drying oven

What temperature and how long should you be heating materials in drying ovens? (1)

at 170 degrees celsius for 2 hours

What type of materials are drying ovens used for and some examples? (3)

• Non temperature sensitive material

• eg. glassware, some dry chemicals