ENVI RONMENTAL DECONTAMINAT ION
and they are known to have more resistance than plastic and polymers to intensive cleaning and disinfection as they are smooth, inert, hard and easy to clean. However, using abrasive materials over time in an effort to clean the stubborn dirt and stains, end up scratching the surfaces and eventually increases the surface roughness leading to formation of microscopic cracks that microorganisms can reside in.8
Another example is the use
of polymers and plastics. Polymers are used due to their low cost, light weight, aesthetics, and corrosion resistance and have replaced metal in medical equipment housings. Most medical equipment housings are not currently designed to withstand disinfection methods. Some polymers can become prematurely brittle when they contact chemicals while under stress. An example of stress on a polymer is when a screw is tightened to connect two components of a housing. Once embrittled, polymers can develop nooks and crannies (microfractures or crazing) that are big enough for microorganisms to reside. This crazing can further propagate into larger cracks and eventually fracture.
Different chemicals can affect a polymer in different ways. A polymer can be resistant to one chemical but easily crack when exposed to another. Moreover, environmental stress cracking is considered a leading cause of plastic failure in healthcare for medical devices and components that come in contact with cleaners, disinfectants, and other chemical agents. It is the premature embrittlement and subsequent cracking of plastic due to simultaneous and synergistic action of stress and contact with chemical agents. Another important example is the use
of coated fabric upholstery throughout healthcare facilities including waiting areas, examination rooms, and patient rooms. Coated fabric upholstery is often specified in healthcare facilities because it is strong, durable and cleanable. Upholstery found in patient and waiting rooms is different from most items cleaned in a healthcare facility in that they cannot be described as having a hard, nonporous surface. Cleaners are designed to be used strictly on hard surfaces, but end up being used on almost all surfaces, including furniture upholstery. The result is that over time, repeated cleanings cause even the best urethane products to break down, usually by delamination of the surface layer.9
Surface roughness and increased microbial adhesion Roughness is the most deployed parameter for describing surface properties and topography in the biofouling literature. Roughness is often used as the sole
MAY 2021
descriptor of surface topography, largely because of its simple calculation, concise presentation, and prevalence in literature. Surface roughness is represented by different quantitative parameters, including Ra (the arithmetical average height), Rq (the root mean square of the height values) and Rz (the difference in height between the average of five highest peaks and five lowest valleys)10, 11
One study by Mireles and colleagues (2016)12
evaluated and compared the effects of some disinfecting agents on different surfaces including sodium hypochlorite hydrogen peroxide, quaternary ammonium compounds and other agents. These active compounds and products were evaluated against different metallic and polymeric surfaces commonly found in hospitals such as: aluminium, stainless steel and galvanised steel, linoleum, polyvinyl
chloride, melamine and vinyl.
The authors demonstrated that pure active compounds such as H2
O2 , NaClO and quats
were more aggressive on metallic surfaces like stainless steel and galvanised steel and can increase roughness and produce future oxide formation and corrosion. On metallic surfaces H2
O2
compound in comparison with aluminium, while quats always shows residues on the surfaces.
The authors recommended a future
surface tension characterisation, as their results assumed the necessity to determine and understand adhesion, hydrophobic and hydrophilic behaviour on each surface and each solution. In addition, they identified black spots since the first application of disinfectant on metallic surfaces, showing that traces of disinfectants kept on holes and scratches decrease the quality of materials.
was the most aggressive active
VIO®
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