Abstract
The bactericidal effect of dioctadecyldimethylammonium bromide (DODAB), a liposome forming synthetic amphiphile, is further evaluated for Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Staphylococcus aureus in order to establish susceptibilities of different bacteria species towards DODAB at a fixed viable bacteria concentration (2.5 × 107 viable bacteria/mL). For the four species, susceptibility towards DODAB increases from E. coli to S. aureus in the order above. Typically, cell viability decreases to 5% over 1 h of interaction time at DODAB concentrations equal to 50 and 5 μm for E. coli and S. aureus, respectively. At charge neutralization of the bacterial cell, bacteria flocculation by DODAB vesicles is shown to be a diffusion-controlled process. Bacteria flocculation does not yield underestimated counts of colony forming units possibly because dilution procedures done before plating cause deflocculation. The effect of vesicle size on cell viability demonstrates that large vesicles, due to their higher affinity constant for the bacteria (45.20 m-1) relative to the small vesicles (0.14 m-1), kill E. coli at smaller DODAB concentrations. For E. coli and S. aureus, simultaneous determination of cell viability and electrophoretic mobility as a function of DODAB concentration yields a very good correlation between cell surface charge and cell viability. Negatively charged cells are 100% viable whereas positively charged cells do not survive.▪The results show a clear correlation between simple adsorption of entire vesicles generating a positive charge on the cell surfaces and cell death.—Campanhã, M. T. N., E. M. Mamizuka, and A. M. Carmona-Ribeiro. Interactions between cationic liposomes and bacteria: the physical-chemistry of the bactericidal action. J. Lipid Res. 1999. 40: 1495–1500.
Highlights
The bactericidal effect of dioctadecyldimethylammonium bromide (DODAB), a liposome forming synthetic amphiphile, is further evaluated for Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Staphylococcus aureus in order to establish susceptibilities of different bacteria species towards DODAB at a fixed viable bacteria concentration (2.5 ؋ 107 viable bacteria/mL)
We determine: 1) dose and time effects on four different bacteria species of clinical importance at a fixed bacteria concentration; 2) effect of vesicle size on E. coli viability; and 3) simultaneous effect of DODAB vesicles on bacteria electrophoretic mobility and viability
As cell concentration is the same for the 4 species, all other experimental conditions being the same, susceptibilities of the 4 bacteria towards DODAB can be compared for 50% and 5% viability (Table 1)
Summary
The bactericidal effect of dioctadecyldimethylammonium bromide (DODAB), a liposome forming synthetic amphiphile, is further evaluated for Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Staphylococcus aureus in order to establish susceptibilities of different bacteria species towards DODAB at a fixed viable bacteria concentration (2.5 ؋ 107 viable bacteria/mL). For E. coli and S. aureus, simultaneous determination of cell viability and electrophoretic mobility as a function of DODAB concentration yields a very good correlation between cell surface charge and cell viability. We determine: 1) dose and time effects on four different bacteria species of clinical importance at a fixed bacteria concentration; 2) effect of vesicle size on E. coli viability; and 3) simultaneous effect of DODAB vesicles on bacteria electrophoretic mobility and viability. An interesting correlation between sign of the cell surface charge and cell viability is found: negatively charged cells are 100% viable whereas positively charged cells do not survive (ca. 0% viability)
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