Antimicrobial textiles: new standards on the horizon

Antimicrobial textile manufacturers face an array of new standards around the world that clarify and specify how they can ensure safety, quality, and proper testing of their products

EN 14683:2014, published in March, specifies the construction, design, performance requirements and test methods for medical face masks

With the growing resistance of bacteria to antibiotics, many industries are seeking new ways to prevent the spread of bacteria, and the incorporation of antimicrobials into garments is just one of many developments in this field. According to the most recent study on antimicrobial coatings, published by research and consulting firm MarketsandMarkets, the global market size for antimicrobial coatings was US$41.5bn in 2012 and it is estimated to have an average annual compound growth rate of 11.8% from 2013 to 2018.

However, the International Organisation for Standardisation (ISO), is now developing ISO/NP 18266, which would create performance requirements and test methods for protective clothing against infective agents. A formal proposal has been made, and the standard is now in ISO’s preparatory stage, and listed as ‘under development’.

Based in Geneva, ISO is the biggest developer globally of voluntary antimicrobial textile standards and test methods, providing industries operating cleanrooms with peer-reviewed guidelines and best practices.

Barrier systems still have living germs on their surface after exposure, whereas antimicrobial surfaces kill these germs

‘The ISO/NP 18266 describes systems and their performance, which represent a barrier against bacteria and viruses,’ said Rainer Steffens, the project leader for this specific standard, who has worked with ISO technical committee TC94 for personal safety – protective clothing and equipment; its sub-committee SC13 for protective clothing; and its working group WG3 for protective clothing against chemicals agents.

‘This performance is tested by ISO methods using dry and wet exposures of the textiles and simply looks at how many such germs are passing through such structures [under] various conditions,’ he said. ‘The main difference is that barrier systems still have living germs on their surface after exposure, whereas antimicrobial surfaces kill these germs.’

While this standard would apply globally, a similar set of rules has existed in Europe since 2003 – which is the reason Steffens, who has also worked with the German Institute for Standardisation (Deutsches Institut für Normung or DIN), said he proposed the standard to ISO. The European Committee for Standardisation’s (CEN) standard 14126 specifies requirements and test methods for re-usable and limited use protective clothing, providing protection against infective agents.

We’re glad to see that the marketplace is starting to recognise the difference

In addition, ISO released a standard ISO 17299 for odour control textile products in April that differentiates them from antimicrobial control standards – a move that antimicrobial producers are applauding. ‘We’re glad to see that the marketplace is starting to recognise the difference,’ said Paul Ford, Chief Executive Officer at Massachusetts-based Sciessent, which makes the Sciessent Lava odour elimination brand and the Agion Antimicrobial brand coatings for textiles, medical devices and sporting apparel in the US, Canada and Europe.

The Agion Antimicrobial coating was recently recommended by the Society for Healthcare Epidemiology of America as an effective control for bloodstream infections when used in Agion-treated catheters.

‘Controlling odour is one thing; controlling antimicrobials is another. And in the best solution, you’re going to have both odour and antimicrobial control,’ said Ford. He welcomed the clarification of which products are antimicrobial or deodorant as a necessary distinction for cleanroom managers.

Ford notes that many odour control products, including Sciessent’s Lava technology, trap and absorb odour particles, then release them during laundering to be washed away. In contrast, Sciessent’s antimicrobial Agion, and other antimicrobials, use silver and other finishes to destroy microbes and bacteria.

In both North America and Europe, the antimicrobial textiles sector has been subject to a significant number of updates in standards and testing procedures. For example, the American Society for Testing and Materials (ASTM) has several voluntary standards. ‘I would say the method that has most affected textile testing in one way or the other is a quantitative method called ASTM 2149, which is a dynamic shake flask method designed to assess the ability for fabrics to inhibit E.coli bacteria,’ said Daniel Price, a member of ASTM subcommittee E35.15 on antimicrobial agents. He noted that the ASTM 2149 test was revised to its current form in early 2013 to introduce results from ‘round-robin’ repeated tests and further developed to apply to a wider list of antimicrobial agents.

Durability is especially important for reusable fabrics such as bedding, uniforms, aprons and lab coats

He added that it is helping companies test for, and improve, antimicrobial durability, even when fabrics have been washed and worn: ‘I have been seeing that as a trend within the industry for proving the durability, [companies are using the] ASTM 2149 [test method] when the fabric is new; after 25 [laundry cycles]; after 50, even after 75.’ This durability is especially important for reusable fabrics such as bedding, uniforms, aprons and lab coats.

Price, who frequently tests medical fabrics, nursing scrubs and military garments in his lab, said companies are investing in silver and new bonding technologies to maintain longer bacteria-repelling abilities. ‘There are many treatments now that are either bound or optimised within or on the polymer that lend themselves to much longer durability,’ he said. ‘And there are some particular silver species within some of these treatments that seem actually to get better the more it’s washed. I know that is counter-intuitive, but those are some of the trends that we’ve seen in our lab.’

He continued: ‘There is metallic silver, which is really put on the threads in high levels. Then there’s the nanosilver. And then there’s silver chlorides, which generally dissolve very quickly; they don’t have the lifetime.’

The biggest challenge is in finding ways to make the active ingredient adhere to the garment or textile

One of the most important areas of focus in the antimicrobial textile sector is developing new ways of maintaining the longevity of antimicrobial systems such as coatings and silver threads. The biggest challenge is in finding ways to make the active ingredient adhere to the garment or textile. ‘To be honest, it did take us a long time to figure out the right binder-cross linker combination [binding mineral ingredients to fabric] to give that durability, especially when you’re looking at a lot of different fabrics, whether its polyester, cotton or nylon,’ Ford said, referring to a technical breakthrough made in 2010.

‘After optimising that, we were able to find one that provides 50-wash durability for the antimicrobials, and then even more so for the odour absorber. So these binder systems are very robust,’ he added.

This bonding and durability technology is an ‘ion exchange mechanism’ that slowly releases the silver or copper in the presence of moisture ions – the sort of environment that grows bacteria.

The testing of such products is aided by ASTM, which has also proposed a guide (ASTM WK31901), under development since 2011, that will advise on how antimicrobial test methods are modified, and help manufacturers determine which tests to use and when. ‘These active ingredients may remain the same but the method of delivering them to textile surfaces continues to be improved. Test methods need to be continually modified to allow for researchers to test these different parameters [and thus] predict the actual performance in use,’ said Robert Monticello, a senior scientific consultant for the US-based International Antimicrobial Council and a technical member of the ASTM international committee E35 on pesticides, antimicrobials and alternative control agents.

Antimicrobial textile standards and testing methods
ISO/NP 18266 Protective clothingPerformance requirements and tests methods for protective clothing against infective agents.Status: Under development
EN 14126 Infective AgentsSpecifies requirements and test methods for re-usable and limited use protective clothing, providing protection against infective agents.Status: Published 2004
ISO 17299-1:2014Specifies the general principle of the deodorant textile products and deodorant testing methods for textile products, such as woven fabric, knit, nonwoven, fibres and yarns, braiding products, tapes and slings.Status: Published 2014
ASTM E2149-13aStandard Test Method for Determining the Antimicrobial Activity of Antimicrobial Agents Under Dynamic Contact Conditions.Status: Revised in 2013
ASTM WK31901New guide on Antimicrobial Agents.Status: Being developed by Subcommittee E35.15, part of ASTM International Committee E35 on Pesticides, Antimicrobials and Alternative Control Agents.
EN 14683:2014 Medical Face MasksRequirements and Test Methods - Describes construction, design, performance requirements and test methods.Status: Published 2014
BS EN 13795:2011+A1:2013Surgical drapes, gowns and clean air suits, used as medical devices for patients, clinical staff and equipment. Covers test methods, performance requirements and performance levels.Status: Updated in 2013

‘Many standards have been written to test multiple types of bacteria,’ he added. ‘These include harmless laboratory strains of bacteria as well as organisms typically associated with hospital acquired infections, such as methicillin-resistant staphylococcus aureus (MRSA) or vancomycin-resistant enterococcus (VRE). It is now well recognised that new antimicrobial agents must have broad spectrum antimicrobial activity,’ he said.

The proposed guide aims to create more predictability in testing for companies. ‘The main problem with antimicrobial testing is the lack of reproducibility between test labs. Two laboratories can run the ‘identical’ test method but may obtain a completely different test result,’ said Monticello. ‘By decreasing the allowed variability within the tests, the manufacturer will see much more reproducibility between laboratories.’

He added that the healthcare sector in particular is harnessing antimicrobial textiles for infection control. ‘With the expanded concern of hospital-acquired infections, the focus on developing new, more relevant methods has expanded. While not directly implicated, it makes practical sense that bacteria can use textiles as vehicles for transport from patient to patient,’ he said. Treating textiles with antimicrobial agents reduces the ability of these textiles to become viable sources of microbial growth and therefore reduces possible cross-contamination, he added.

The healthcare sector in particular is harnessing antimicrobial textiles for infection control

Meanwhile, the EU’s CEN has several arms dedicated to voluntary antimicrobial and infection control standards in textiles. Technical committee (TC) 205 working group 15 on wound dressings has proposed a standard that would specify requirements and test methods for both microbiocidal and microbiostatic dressings, which is expected to be voted on by members in July 2015.

TC 205 working group 14 covers standards for surgical clothing and drapes, and medical face masks. A new standard (EN 14683:2014) published in March, gives comprehensive specifications for the construction, design, performance requirements and test methods for medical face masks. The standards, for masks intended to ‘limit the transmission of infective agents from staff to patients during surgical procedures and other medical settings’, state that a medical face mask with an appropriate microbial barrier can be effective at reducing the emission of infective agents from asymptomatic carriers or patients with clinical symptoms.

A standard updated in 2013 (EN 13795:2011+A1:2013) provides general test methods and performance requirements for manufacturers, and ‘gives information on the characteristics of single-use and reusable surgical gowns, surgical drapes and clean air suits used as medical devices for patients, clinical staff and equipment, intended to prevent the transmission of infective agents between patients and clinical staff during surgical and other invasive procedures.’

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