Bactericidal activity of liposome-encapsulated nisin against Streptococcus mutans. Exponentially proliferating cultures of S. mutans 10449 (turbidity of 0.02 at 600 nm) were incubated for 4 h at 37°C in 0.2 ml of Todd Hewitt Broth in the presence of nisin-loaded liposome, an equivalent concentration of naked nisin, or buffer. A minimum inhibitory concentration (MIC) assay as indicative of the bactericidal activity of individual samples was quantified using resazurin dye. Symbols indicate the lipid formulations of liposomes and controls. *P < 0.05 indicates a significant difference of MIC values of the reaction mixtures containing DPPC/PS-encapsulated nisin compared with those of the control liposome, nisin-loaded DPPC. Values represent the mean of triplicate replications and the bars represent the standard deviation of sample means.