What is sterilization?

Sterilization is the process of completely eliminating all microorganisms, including the most resistant bacteria and spores. It represents the highest level of microbial control and is essential in laboratory and healthcare environments where absolute sterility is required.

Why sterilization is difficult to achieve and verify? 

Sterilization is not only difficult to achieve, but also challenging to prove.

Although many chemical agents, both organic and inorganic, can kill microorganisms, they are not always fully effective and may leave undesirable or toxic residues.

What are the limits of radiation-based sterilization? 

Radiation methods, such as ultraviolet and ionising radiation, act as biocides by disrupting DNA and preventing microbial replication.

However, ultraviolet radiation does not provide the same level of effectiveness or ease of validation as moist heat sterilization. When absolute sterility is required, steam remains the preferred method.

How does steam sterilization work? 

Microorganisms generally become more active as temperature increases. Most, though not all, are destroyed above 80 °C. Some, such as prions, require higher temperatures and longer exposure times.

Steam sterilization works through an efficient heat transfer process:

• Steam condenses on cooler surfaces, including microorganisms
• During condensation, it releases approximately 2,500 joules per gram of steam
• This rapidly raises the temperature to the level at which microorganisms are destroyed

Compared to other heating methods, steam is more effective because:

• It transfers heat more efficiently
• It avoids insulating boundary layer effects seen with dry hot air