4-Staphylococcus -aureus -Bactericidal and sporicidal performance of a polymer-encapsulated chlorine dioxide-coated surface

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Bactericidal and sporicidal performance of a polymer-encapsulated chlorine dioxide-coated surface 

W.K. Leung1,2, A.P.S. Lau3 and K.L. Yeung1 1 Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China 2 Environmental Engineering Program, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China 3 Institute for the Environment, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

ORIGINAL ARTICLE 

Abstract Aims: 

To investigate the physical characteristics and the bactericidal and sporicidal potential of a polymer-encapsulated ClO2 coating. Methods and Results: An antimicrobial coating based on polymer-encapsulated ClO2 was developed. A low viscosity, water⁄ oil ⁄water double emulsion coating was formulated for easy on-site application. Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus were applied onto the coating to study the bactericidal capabilities of the coating. The bactericidal performance of the coating increased when the contact time with the tested bacteria increased. Over 99% of the E. coli, Ps. aeruginosa, B. subtilis were killed with a contact time of 30 min. Although endospores of B. subtilis are more resistant, about 75% of the spores were killed after 72 h on the coating. Moreover, a sustained release of gaseous ClO2 was achieved to maintain about 90% removal of B. subtilis with a 10-min contact time during a 28-day study period. The coating also exhibits antiadhesive properties against bacteria. 

Conclusions: A polymer-encapsulated ClO2 coating with sustained release of ClO2 and promising bactericidal and sporicidal features was tested for 28 days. Significance and Impact of the Study: This study provides a new direction for developing polymer-encapsulated ClO2 coatings that possess persistent bactericidal and sporicidal properties......

......The coating also demonstrates consistent bactericidal potential. The ClO2 released from the coating killed over 90% of the E. coli, Ps. aerugenosa, B. subtilis, and Staph. aureus and about 10% of B. subtilis endospores with a contact time of 30 min. The amount of B. subtilis killed was comparable with that killed after exposure to 300 ppm ClO2 solution. The relative susceptibility of B. subtilis spores and the range of bacteria killed followed with the trend reported by Russell (2003). Gram-negative E. coli was most susceptible and endospores of B. subtilis were the least susceptible (Figs 2 and 3). 

Staphylococcus aureus was the least susceptible to ClO2 among the tested vegetative species. 

Staphylococcus aureus also exhibited similar low susceptibility to a hypochlorite (i.e. bleach) solution (data not shown). This may be related to the presence of carotenoid pigments in Staph. aureus that are antioxidative and provide the bacteria with some degree of protection from oxidizing biocides (Clauditz et al. 2006). Despite the different susceptibilities of the bacteria to polymer-encapsulated ClO2, the bactericidal and sporicidal performance generally increased as the contact time was prolonged. 

This trend favours the use of the encapsulated coating as an antimicrobial surface. Under ambient conditions, droplets or fomites from whatever source will be deposited onto surfaces and remain on the site until they are transferred to other surfaces or objects after contact. This means that there is ample time for the ClO2 to act on the species resting on the coating. We speculate that the bactericidal or sporicidal activity is caused by multiple actions of the coating. Primarily, both dissolved and gaseous ClO2 is released through diffusion from the ClO2 encapsulated in the polymer matrix. In addition, the coating is rehydrated by droplets or fomites upon deposition. This rehydration destabilizes the outermost membrane film of the coating, resulting in its rupture and rapid flooding of the contact area with the encapsulated ClO2. The release is sustained by the difference in the osmotic pressures between the exterior and interior.......