Sterilization of Media and Equipment

Question 1

What is the process of rendering a medium or material free of all forms of life.

Answer 1

Sterilization

Question 2

A method of sterilization where items are exposed to steam at 121°C and 15 psi for 15 minutes or longer. Microorganisms, including endospores, are unable to survive under these conditions.

Answer 2

Autoclaving

Question 3

This method, such as using an electric oven set between 160 and 170°C, is used for items like glassware because steam can etch glass and leave it damp. It is effective but requires longer exposure times, typically about 2 hours.

Answer 3

Dry-heat sterilization

Question 4

If media cannot withstand heat, it can be sterilized by passing it through this methos, which physically removes bacteria and larger microorganisms from the solution. Sintered glass filters with ultrafine fitted disks and Seitz asbestos-pad filter funnels are effective options.

Answer 4

Bacteriological filter

Question 5

What is the most popular approach for sterilization using filters?

Answer 5

The most popular approach for sterilization using filters is the use of specially prepared sterile membranes made of cellulose or polycarbonate, with pore sizes typically around 0.22 µm. Various commercially available devices, like filter flasks with vacuum or syringes with positive pressure, are used to force liquids through these membranes for sterilization.

Question 6

Why is it crucial for autoclaves to expel all air from the chamber before sterilization?

Answer 6

Autoclaves must expel all air from the chamber before sterilization to ensure that only steam is present. Air pockets can compromise sterilization effectiveness by creating areas where microorganisms can survive.

Question 7

What is the consequence if the temperature in the oven for dry-heat sterilization rises above 180°C?

Answer 7

If the temperature in the oven rises above 180°C, any cotton or paper present will char, potentially leading to contamination and rendering the sterilization process ineffective.

Question 8

What are the pore sizes of the membranes typically used for sterilization by filtration?

Answer 8

Membranes used for sterilization by filtration typically have pore sizes around 0.22 µm, which effectively remove bacteria and larger microorganisms from the solution.

Question 9

What are some commercially available devices used for membrane sterilization?

Answer 9

Various commercially available devices, such as filter flasks with vacuum or syringes with positive pressure, are used for membrane sterilization of both large and small volumes of liquid.