Adhesion and viability of waterborne pathogens on p-DADMAC coatings

The attachment of waterborne pathogens onto surfaces can be increased by coating the surfaces with positive charge-enhancing polymers. In this paper, the increased efficacy of polydiallyldimethylammonium chloride (p-DADMAC) coatings on glass was evaluated in a parallel plate flow chamber with the use of waterborne pathogens (Raoultella terrigena, Escherichia coli, and Brevundimonas diminuta). p-DADMAC coatings strongly compensated the highly negative charges on the glass surface and even yielded a positively charged surface when applied from a 500 ppm solution. Whereas none of the strains adhered from water to glass due to electrostatic repulsion, R. terrigena and E. coli readily adhered in high numbers to p-DADMAC coated glass slides applied from 1, 100, or 500 ppm aqueous solutions. B. diminuta only adhered to a positively charged p-DADMAC coating applied from a 500 ppm solution. In addition, all p-DADMAC coatings indicated strong contact killing with the bacterial species used in this study by live/dead staining techniques. In summary, this paper demonstrates the potential of p-DADMAC coatings to strongly enhance bacterial adhesion. Moreover, once adhered, bacterial viability can be reduced by the positively charged ammonium groups in the coating.