Removal of Bacteria from Solid Surfaces by Wiping with Nonwoven Fabrics

Healthcare associated infections are responsible for substantial patient morbidity, mortality and economic cost. Infection control strategies for reducing rates of transmission include the use of nonwoven wipes, with or without a biocidal liquid, to remove pathogenic bacteria from frequently touched surfaces. Considerable research has been conducted on the role of biocides in disrupting microbes such as bacteria, but less is known about the influence of wiping surfaces with nonwovens regarding their removal. This research considers the role of intrinsic and extrinsic factors on the removal of bacterial contamination from model healthcare surfaces. The extent to which systematic changes in wipe fibre surface energy and nano-roughness influence removal of bacteria from a polymer surface in dry wiping conditions was studied. Nonwoven wipe substrates composed of two commonly used fibre types, lyocell (cellulose II) and polypropylene (PP), with different surface energies and nano-roughnesses, were experimentally manufactured. The surface energy and nano-roughness of lyocell substrates were modified by either oxygen or hexafluoroethane plasma treatment. Static wiping of an inoculated surface under dry conditions produced bacterial removal efficiencies of between 9.4 colony forming unit (CFU) % and 15.7 CFU % versus control, with no significant difference (p 50 CFU % versus static wiping (p <0.05), depending on fibre type and bacterium. Under dynamic wiping conditions, nonwoven wipe substrates with a surface energy closest to that of the contaminated surface produced the highest E. coli removal efficiency, while the associated increase in fibre nano-roughness abrogated this trend with S. aureus and E. faecalis. Considering both intrinsic and extrinsic factors of wiping and design factors on the removal of pathogenic bacteria, the single most important parameter affecting bacterial removal efficiency was impregnation with biocidal liquid (p <0.05). However, dynamic wiping in the dry state and with water alone without biocide still resulted in substantial removal. Bacterial removal was therefore not conditional on the presence of a biocide. For 100% lyocell wipes impregnated with biocidal liquid, removal of E. coli, S. aureus and E. faecalis improved by increasing the fabric basis weight and hand weight wiping pressure to their maximal values (150 g.m-2 and 13.80 kN.m-2 respectively). For 100% polypropylene wipes, the same conditions maximised the removal efficiency of S. aureus. For E. coli and E. faecalis, a reduction in the hand weight wiping pressure to 4.68 kN.m-2 was required to maximise the removal efficiency with 100% polypropylene. Generally, the lyocell wipes were more effective in removing bacterial contamination than 100% polypropylene wipes. The removal and destruction of pathogenic bacteria partly by wiping relies on their transfer to fibre surfaces within the wipe. The extent to which the surface properties influences specific bacterial removal was investigated in terms of polymer composition and surface roughness, as well any residual antimicrobial activity conferred to the surface by the biocide. It was determined that there was no significant difference in removal of E. coli, S. aureus and E. faecalis from plastic, ceramic or metal surfaces by either 100% lyocell or 100% polypropylene nonwoven wipes (p <0.05) during wet wiping. No significant residual antimicrobial activity was seen form the biocide deposited on clinical surfaces after wiping (p