skip to Main Content

Evolution of sterilisation

We’ve come a long way since the days of demons and evil spirits being thought to be the cause of plagues and infection. It was in fact Hippocrates of Cos (460-377 BC), who first separated medicine from philosophy and refuted the idea of disease being a punishment for sin, what a relief!


Scientific developments for sterilisation remained a mystery until Louis Pasteur’s work from 1862 was accepted in later years. Initially searching for a solution to the spoilage of wine and beer, he identified that bacteria could be killed at 120 degrees Fahrenheit. Upon applying this practice to medical instrument cleaning, Pasteur coined the technique of boiling instruments to kill microorganisms. It was his work that inspired Charles Chamberland – (a pupil of Pasteur’s) to turn the original autoclave, a pressure cooker, into a standard medical tool in 1879.

Supply and demand

From their beginnings as basic mechanical machines, autoclaves have come a long way. Now computerised, they are a vital component in hospitals, laboratories and clinics. With the importance of sterilisation firmly identified, the autoclave market has since boomed with projections estimating it to reach $7.5 billion by 2023.

This demand is mostly fuelled by the increasing incidence of HAIs, growing ageing population and the higher number of clinics outsourcing sterilisation to external facilities.

A variety of methods

Today transmissible agents like spores, bacteria and viruses can be eliminated through methods such as ethylene oxide (gas), chemical (cold) and dry heat sterilisation, though the technique of choice in most medical environments is steam sterilisation.

Which autoclave is best?

With a saturated market of steam sterilisers ranging from all shapes, sizes, specs and prices, it can be a minefield trying to identify which is best for you. Clinics must consider their specific needs, the frequency of cycles required per day and not to mention their budget.  Thankfully, autoclave varieties can all be categorised into one of three types: Class B, Class S and Class N – which often helps narrow the search a little.

A simple overview of the differences:

  • Class B – used for sterilising all objects (solid & hollow instruments, textiles, porous items, both packaged and un-packaged loads)
  • Class S – used for sterilising unpackaged, uncomplicated hollow or solid instruments
  • Class N – used for sterilising only un-packaged solid instruments

Naturally, Class B autoclaves are the most popular as they provide the most flexibility.

Uncertainty, human error and contamination

Reducing cross-contamination by autoclaving is thought to be one of the most important methods in breaking the chain of infection. However, as is apparent in regular media updates, sterilisation isn’t always guaranteed. Prions such as those associated with Creutzfeldt–Jakob disease have been identified to survive the autoclave along with many external factors that can contribute to sterilisation failure.

This is a multifaceted problem which can result from a variety of causes including improper precleaning of instruments and inadequate equipment maintenance. Unfortunately, many issues are due to human error and are unlikely to be eliminated unless a fully automated system is created.

However, thanks to modern technology, we are being introduced to alternative ways to avoid contamination and are constantly refining infection control practices in healthcare.