Role of surface energy and nano-roughness in the removal efficiency of bacterial contamination by nonwoven wipes from frequently touched surfaces

Abstract

Healthcare associated infections (HCAIs) are responsible for substantial patient morbidity, mortality and economic cost. Infection control strategies for reducing rates of transmission include the use of nonwoven wipes to remove pathogenic bacteria from frequently touched surfaces. Wiping is a dynamic process that involves physicochemical mechanisms to detach and transfer bacteria to fibre surfaces within the wipe. The purpose of this study was to determine the extent to which systematic changes in fibre surface energy and nano-roughness influence removal of bacteria from an abiotic polymer surface in dry wiping conditions, without liquid detergents or disinfectants. Nonwoven wipe substrates composed of two commonly used fibre types, lyocell (cellulosic) and polypropylene, with different surface energies and nano-roughnesses, were manufactured using pilot-scale nonwoven facilities to produce samples of comparable structure and dimensional properties. The surface energy and nano-roughness of some lyocell substrates were further adjusted by either oxygen (O2) or hexafluoroethane (C2F6) gas plasma treatment. Static adpression wiping of an inoculated surface under dry conditions produced removal efficiencies of between 9.4% and 15.7%, with no significant difference (p < 0.05) in the relative removal efficiencies of Escherichia coli, Staphylococcus aureus or Enterococcus faecalis. However, dynamic wiping markedly increased peak wiping efficiencies to over 50%, with a minimum increase in removal efficiency of 12.5% and a maximum increase in removal efficiency of 37.9% (all significant at p < 0.05) compared with static wiping, depending on fibre type and bacterium. In dry, 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.

Factors affecting removal of bacterial pathogens from healthcare surfaces during dynamic wiping

“…Therefore the likelihood of either a bacterial "kill" on the contaminated surface or bacterial removal from the contaminated surface is higher with higher surface density. It has previously been shown that bacteria interact with and adhere directly to the fibres in dry wipes (14). Therefore, if more fibres are present at the wipe-contaminated surface interface, there is a greater likelihood of bacterial adhesion and removal.…”

“…As reported in these experiments, greater fibre surface area is provided at the interface between the wipe and contaminated surface. As the wipe surface density increases, there will be more surface provided for bacterial adhesion (14).…”

“…protein), the salts also present in the bovine serum albumin will deposit on the PMMA surface, decreasing the wetting tension of the PMMA surface (14).…”

“…Strains were cultured according to previously published methods (14). These were selected as examples of pathogenic bacteria.…”

“…The porosity is an important influence on the total liquid absorptive capacity of the wipe. It has been shown that the mechanical action of wiping with a dry nonwoven fabric is capable of removing some of the bacteria present on a surface (14). Impregnation with an aqueous biocidal formulation substantially improves the removal of particles up to a limit, depending on the absorptive capacity of the fabric (15).…”