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Time for a sterile discussion: What sterilisation option is right for your business?

Teknomek Ltd

Sue Springett, commercial manager at Teknomek

The rigorous standards on contamination prevention and control laid out by the UK Medicine and Healthcare products Regulatory Agency (MHRA) means the maintenance of sterile environments, such as clean rooms, is a significant and ongoing concern.

Given it can take upwards of twelve months just to finalise the design of a clean room, the risk of an audit failure makes each clean down critical. As such, ensuring that environment remains sterile is an absolute priority in the day to day running of a facility. By necessity, cleaning processes are both time-consuming and a significant operating expense.

However, choosing the right sterilisation option, coupled with specialist support materials and furniture, can considerably diminish that pain point. With so many options available, it can be hard to decide whatís right for any given context.

Wash and go?

It might be hard to believe, but once upon a time industry regulators deemed a Ďsimpleí wash down acceptable. This certainly wasnít an easy option though and required meticulous manual work with diluted cleaners. However, so long as each area of the clean room was within reach a clean cloth or brush, then that was sufficient. Those days are, of course, long gone and thatís no bad thing. Given the considerable effort that went into this approach I very much doubt thereís much nostalgia for simpler times! The reality is this was hugely inefficient, just consider the hours taken up each day, week, month or year and then marry this with the considerable operating expenses incurred.

Back to the future

One of the industryís most widespread sterilisation technologies has been with us since the mid-nineteenth century, the autoclave. This piece of kit that can be found in almost any lab or clean room and is available in a wide-range of sizes to suit different applications. The autoclave generates no by-products and is non-toxic but its long-standing success stems from its versatility. It can be used to sterilise a wide range of products and is well-suited to deep-cleaning re-usable items such as lab instruments and utensils.

Larger models can be used to sterilise numerous pieces of equipment in a single cycle, as well as bulkier items, including anti-bacterial matting, or storage systems and furniture that can be dismantled for sterilisation.

However, there are downsides to the autoclave, primarily its ferocity and the fact it is a wet heat. An autoclave operates at 121 įC (249 įF), which means you have to be very careful what equipment you do run through it. Itís effectively a steam cleaner, so it is essential that the material of the product being autoclaved is resilient enough to survive that process, materials such as plastics, polyethylene or silicon may be destroyed or become deformed.

Equally steam does offer certain benefits, it has a high-energy transfer capacity, which makes it a safe option for eliminating organic compounds. As such, autoclaves are typically used for scenarios in which you have to be 100 percent certain youíve neutralised micro-organisms.

Although autoclaves are comparatively expensive to run, the use of wet heat is significantly quicker and uses less energy than dry heat sterilisers. However, having the option to sterilise equipment for re-use on an ongoing basis generally outweighs the running costs. An additional benefit is because itís a contained process, the operator can continue to work within the cleanroom throughout the sterilisation process.

This is the third century in which the autoclave has been a standard feature within this industry and its longevity speaks volumes. Itís a safe and versatile option for use in numerous applications and we still see new autoclavable products coming to the market.

New(ish) and rad-ical

Radiation-based sterilisation techniques, for example UV or gamma radiation, are also popular options for destroying bacteria. The key advantages over the autoclave are these methods do not produce heat or moisture, nor leave any residue. Perhaps most significantly, they can also be used on a broader range of materials, including plastics and even adhesives.

The gamma sterilisation process uses Cobalt 60 radiation to kill bacteria by breaking the covalent bonds of bacterial DNA. Of course this does bring with it a health and safety risk because it will do the same to any DNA. There are also some practical disadvantages to radiation-based methods, UV lamps have a limited radius and items to be sterilised using gamma radiation must be bagged. This places a limit on the size of equipment that can be treated by either option. That said, more and more disposable consumables now come pre-packaged in plastic to support gamma sterilisation.

Itís a gas

The third option is chemical sterilisation and this is most typically hydrogen or chlorine-based. Notably, Vaporised Hydrogen Peroxide (VHP) is becoming a particularly popular method for onsite sterilisation. VHP is a good choice for equipment that may not be tough enough to withstand the highest temperatures of an autoclave or can be damaged by irradiation. It has a short cycle time compared to other methods, a full sterilisation in a VHP chamber can take under half an hour.

Although it does offer some clear benefits, the main downside to chemical options is the risk to health and safety. Although VHP isnít anywhere near as carcinogenic as chlorine-based equivalents and its only residue is water, it is still classified as being dangerous to human health. Therefore, the design for facilities making use of chemical sterilisation methods have to factor in specialist - and very expensive - ventilation systems.

While VHP is undoubtedly the quickest and most efficient way to sterilise in a single treatment, that doesnít necessarily make it appropriate for all use cases. The additional costs involved in staff training and the time for post VHP ventilation may make it less attractive.

New approaches

Certain segments of the pharma industry may not even need to consider on-site sterilisation as the trend towards single use pre-sterilised consumables grows. While the use of disposable equipment may be a sensible strategy for decreasing contamination risks for the longer-term, itís is not without its own problems. As well as being bad for the environment, this throwaway culture is both expensive and impractical for businesses that demand the most rigorous sterilisation regimes, or need to sterilise larger items, such as furniture.

There are pros and cons to any method, a simple rule of thumb is to design your cleanroom around the sterilisation techniques that the application will most typically require. However, selecting the wrong sterilisation method can unnecessarily prolong the cleaning process or even reduce the lifespan of equipment.

Do sweat the small stuff

From this perspective, itís really not worth cutting corners when it comes to furniture and other support kit. A practical approach to take during the procurement process is to work backwards from the practicalities of the cleaning regime. There are certain considerations that apply in general, for example is hygiene factored into the design? Intelligently-designed furniture and equipment can reduce clean down time just by offering easier access - so is it easy to get to the back or underneath? Also, be aware of design flaws that could harbour dirt and micro-organisms: check for dirt traps - such as gaps, ledges or folds Ė and look for ledges or other flat surfaces can collect water (and germs) if there arenít clear drainage points, and pay particular attention around taps.

Once you satisfied the basics, consider the practicalities of the sterilisation process youíve opted for. For example, if youíre going to use an autoclave can the furniture you choose be quickly and easily disassembled and reassembled? If youíre using particularly aggressive chemical sterilisation, such as chlorine, it would be advisable to invest in furniture made with 316 grade stainless steel. This has higher nickel content backed by the addition of molybdenum for an increased corrosion resistance, including chloride contents up to 500 mg/l.

In real terms, any sterilisation technique is going to take a toll on furniture and support kit. Itís for this reason that stainless steel has become such a popular option throughout the pharma sector. As well as being durable, itís also chemically inert and easy to clean. As previously detailed 316 grade tends to be used for the very toughest cleaning regimes, but 304 grade stainless steel is a good all-rounder and is most commonly found in clean room applications.
Regardless of what sterilisation regime you do finally settle upon, it is also worth remembering hygiene standards donít start and end at the cleanroom. The MHRA auditor will be assessing hygienic standards throughout a facility, the design of changing rooms, washing facilities and so-on, should be as well considered as a clean room. An audit can be failed in any part of a facility, your end goal should always be to establish and maintain a business-wide hygiene culture.
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