Adequate surface decontamination is essential to prevent the spread of healthcare-associated infections (HCAIs)[1-5]. As evidence for decontamination of environmental surfaces has grown, surfaces in a healthcare setting are being exposed to disinfectants more frequently in the fight against HCAIs.

Recent alerts from both UK and Australian regulatory bodies, highlighted increased risk of damage to plastic surfaces if compatible disinfectants are not used[6-8]. The focus of these alerts is primarily on disinfectants and use but the materials used in construction of these surfaces have a huge role to play. Incompatibility of detergent and disinfectant wipes with plastic surfaces has been reported on a number of healthcare surfaces and equipment including tympanic thermometers, patient monitors, and infusion pumps[7].

Healthcare practitioners are now disinfecting more surfaces than ever before but, at the same time, manufacturers increasingly tend towards utilising cheaper polymers in construction of healthcare equipment[9]. The change in infection prevention techniques has led to more rigorous cleaning of items that were not designed for exposure to disinfectants in the same way as products designed solely for healthcare use. These include light switches, plug sockets and phone handsets, made from less durable polymers that may experience premature failure following frequent disinfection.

When surface materials are incompatible with the disinfectants used to clean them, it can lead to lasting damage and premature failure: they can react in a way that breaks down the plasticity and causes them to become brittle and crack – this is known as environmental stress cracking[10].

In addition to loss of function, damaged surfaces can become increasingly hard to disinfect and therefore harbour microorganisms.

There are two primary factors that have led to an increase in environmental stress cracking throughout healthcare: practitioners are disinfecting more surfaces than ever before and equipment manufacturers are moving away from durable metals and plastics towards cheaper polymers[9]. These cheaper polymers are susceptible to environmental stress cracking caused by repeated exposure to the chemical disinfectants used to help prevent healthcare-associated infections.

Disinfectants are required to adhere to strict standards of efficacy, stability and safety before regulators will allow products to enter the market. These same standards do not apply to materials selected for construction of healthcare equipment – particularly of plastic surfaces commonly found in domestic environments, such as plugs and power sockets.

The best way to prevent material incompatibility is to have a systematic approach to equipment procurement. We’ve put together a checklist of questions (which can be found in the Resources tab) to ask manufacturers to ensure they have provided adequate decontamination instructions. These are important questions for a manufacturer to answer: evidence-based infection prevention practices are vital to ensure patient safety, you should not be forced to compromise your environmental cleaning practice because equipment manufacturers have failed to perform compatibility testing.

If you’re in the UK, the MHRA requires that equipment manufacturers provide this information; if you feel it is not forthcoming, raise concerns with both the manufacturer and the MHRA.

Elsewhere, local regulatory bodies differ in the amount of compatibility data they require from equipment manufacturers; if you’re unsure what the manufacturers are obliged to provide, contact your regulator.

Whilst the onus is largely on equipment manufacturers to select appropriate polymers, it’s important to select disinfectant products with both a strong evidence base and robust compatibility data. Whilst Australia’s medical device regulator, the TGA, has issued an alert on the use of Quaternary Ammonium Compounds (QACs), evidence suggests the causative agents are more likely to be amines – hydrocarbon derivatives of ammonia.

We have seen that some healthcare environmental plastics, often electrical outlets, are now made from polycarbonates. Polycarbonates are easily damaged by amines – through a mechanism called aminolysis – leading to cracking of the plastic[12]. The ability of amines to breakdown polycarbonate is so great that they have been studied as a potential method for recycling plastics[13]. Amines are sub-classified as primary, secondary and tertiary based on the degree of hydrocarbon substitution – it’s this substitution that interacts with plastic surfaces. This issue is not limited to polycarbonates: amines have been found to cause chemical weakening of PET, PVC and rubber[14].

Amines with four hydrocarbon substituents are positively charged and exist as ‘permanent cations’ – referred to as QACs – this makes QACs morphologically and functionally distinct from primary, secondary and tertiary amines. The reactivity of amines depends upon the presence of a free electron pair on the nitrogen; QACs do not have these and therefore do not undergo aminolysis reactions in the same way.

Quaternary Ammonium Compounds are comparatively unreactive and have good surface compatibility compared with other disinfectants[15].

Additionally, because they exist as permanent cations, they act as detergents, as well as disinfectants, and do not diffuse readily across biological membranes – making them ideal for human and animal disinfection.[16]

The most likely source of amines in a hospital environment is not from use of QACs, but from chlorine-based disinfectants: reactions between chlorine-based disinfectants and organic matter produce, amongst other things, chloramines[17]. Chloramines are highly reactive amines which can be responsible for aminolysis of plastic surfaces.

In addition, some disinfectant manufacturers use amines to supplement the disinfectant activity of their QAC-based formulations. GAMA Universal-range surface disinfection products are QAC-based and have a comparatively neutral pH, making them compatible with a broad range of surfaces. Third-party testing carried out, on both the Universal and Sporicidal wipes, showed they do not produce amines in their eluate and so do not cause environmental stress cracking through aminolysis. You should always be aware of the active biocides in your disinfectant formulations and ensure there are no ‘hidden’ agents that may cause surface compatibility issues.

GAMA Healthcare collaborates with manufacturers of healthcare equipment to test compatibility, produce decontamination procedures, and inform polymer choice for new products; you can find a list of equipment for which GAMA products are approved for use in the Resources tab.

Regulatory body recommendations, such as those issued by Australia’s TGA, have the potential to influence Infection Prevention and Control (IPC) policies. Changing disinfectant products with inadequate scientific evidence can lead to sub-optimal cleaning – placing patients, staff and visitors at risk.

Reducing incidence of healthcare associated infections should always be priority; clear clinical evidence is essential before any IPC policy is changed.

QACs were identified as the key component of disinfectants used on items that were showing signs of material incompatibility. Despite the TGA's conclusions that the QAC, benzalkonium chloride, was the causative agent, there was no evidence to support its causative role in the damage seen.

QACs are a popular choice for healthcare disinfectants because of their ability to also act as detergents; this allows manufacturers to formulate products that disinfect and clean in one step – vital for improving staff compliance and ensuring Infection Prevention and Control (IPC) policies are carried out. They have been shown to be relatively unreactive and have good surface compatibility compared with other disinfectants[3].

Benzalkonium chloride is commonly used at 0.5% in disinfectants, considered to be safe at concentrations less than 5% by the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP) and is used globally as a surfactant/disinfectant. Despite its global use, reports of incompatibility seem to be primarily limited to Australia. This suggests that the material incompatibility observed in the infusion pumps is unlikely to be due to benzalkonium chloride.

A material incompatibility test, carried out by ExcelPlas on failed polycarbonate plug sockets, supports the hypothesis that QACs are not the cause of the damage. Data identified the causative agents as three amines deposited by disinfectants on the surface of the plug sockets.

Polycarbonates are easily damaged by amines – this process is so effective that it has been investigated as a potential method for recycling plastics[4,5]. This issue is not limited to polycarbonate: amines have been found to cause chemical weakening of PET, PVC and rubber[6].

Amines are hydrocarbon derivatives of ammonia and are sub-classified as primary, secondary and tertiary based on the degree of hydrocarbon substitution. It is this substitution that reacts with plastic surfaces to cause damage.

QACs are amines with four hydrocarbon substituents, are positively charged and exist as ‘permanent cations’. This makes QACs morphologically and functionally distinct from primary, secondary and tertiary amines. The reactivity of amines depends on the presence of a free electron pair on the nitrogen; QACs do not have this and therefore do not undergo chemical reactions in the same way. There is a vast amount of supporting evidence for the wide use of QACs as disinfectants. Incompatibility is unlikely to be caused by QACs but by the reactions that occur with primary, secondary and tertiary amines. The most likely source of amines in a hospital environment is, not from use of QACs but, from chlorine-based disinfectants; reactions between chlorine-based disinfectants and organic matter produce, amongst other things, chloramines[7]. These are highly reactive amines which can be responsible for chemical attack of plastic surfaces.

As a disinfectant manufacturer that places great importance on scientific process, GAMA Healthcare has more equipment compatibility data that any other manufacturer. Surface compatibility is a key priority; we work closely with healthcare equipment manufacturers to ensure our products are compatible.

When damaged polycarbonate plug sockets were tested by ExcelPlas, they found that the causative agents were amines. Nuclear Magnetic Resonance (NMR) analysis of Clinell Universal Wipes demonstrated no presence of amines in their eluate. The plug socket manufacturer stated that the polycarbonate can withstand 2% peracetic acid and 30% hydrogen peroxide. Clinell Sporicidal Wipes generate considerably more dilute concentrations of these (0.2%-0.3% and 0.6%, respectively). Evidence does not support the hypothesis that Clinell Universal and Sporicidal are the causative agents in this case.

GAMA supports the TGA in raising awareness of the issue of incompatibility and requesting review of decontamination processes to ensure all products used to clean and decontaminate items in healthcare are compatible with, and used in accordance with, manufacturers’ instructions. Caution should be taken in targeting the disinfection process as a predominant issue rather than the need to use compatible products in an approved manner.

Evidence to support these conclusions is vital if they are to justify change in IPC policies towards sub-optimal techniques. It is essential that healthcare equipment is constructed from materials proven robust enough to tolerate regular disinfection. The responsibility lies with both the disinfectant manufacturer and the healthcare equipment/product manufacturer collaborate to ensure compatibility. Selection of wipes is just as important as the healthcare equipment that is chosen. Infection prevention efforts may be compromised if both are not considered in conjunction.

The Medical Device Directive and the Therapeutic Goods Administration (TGA) requirements stipulate that the onus is on the equipment manufacturer to provide a validated cleaning/disinfection program for their reusable surface. Some manufacturers are addressing these issues, however, compatibility data remains lacking. Further studies must be carried out to develop clear standards of material selection and disinfectant formulation.

The best way to prevent material incompatibility is to have a systematic approach to equipment procurement. GAMA has put together a checklist of questions (which can be found in the Resources tab) to discuss with manufacturers to ensure they have provided adequate decontamination instructions. These are important questions for a manufacturer to answer: evidence-based infection prevention practices are vital to ensure patient safety. Environmental cleaning practice should not be compromised because equipment manufacturers have failed to perform compatibility testing.

GAMA Healthcare collaborates with manufacturers of healthcare equipment to test compatibility, produce decontamination procedures, and inform polymer choice for new products; you can find a list of equipment for which GAMA products are approved for use in the Resources tab.