Biofilm removal caused by chemical treatments

Biofilm protein removal by a variety of chemical treatments was investigated. Binary population biofilms of P. aeruginosa and K. pneumoniae were grown in continuous flow annular reactors for 7-9 days prior to a 1-h treatment period. Treatments that caused removal of more than 25% of the biomass (as total protein) included NaCl and CaCl2, two chelating agents (EDTA and Dequest 2006), surfactants (SDS, Tween 20, and Triton X-100), a pH increase, lysozyme, hypochlorite. monochloramine. and concentrated urea. Treatments that caused little removal (less than 25%) included a control. MgCl2, sucrose, nutrient upshifts and downshifts, and a pH decrease. The amount of biofilm protein removal and the reduction in viable cell numbers in the biofilm were not correlated. Some treatments caused significant killing but not much removal while other treatments caused removal with little killing. These results underscore the fact that biofilm removal and killing are distinct processes. The chemical diversity of agents that bring about biofilm removal suggests that multiple interactive forces contribute to biofilm cohesion. No pattern of differential removal of the two microbial species could be discerned. (C) 2000 Elsevier Science Ltd. Ail rights reserved.