[Synergy, addition, indifference, antagonism and dominance. Dominance and antibiotic combination]

Six strains of Staphylococcus aureus have been studied using an original method which associate the chessboard's technique to that of bactericidal kinetic's. Associations of pefloxacin and rifampicin, vancomycin and fosfomycin are analysed, and result of each concentration's connection is expressed, at 1.5, 3,5 and 24 h, by a three dimensional representation, which facilitate the phenomenon's dynamic. Interpretation of these diagrams can show the classical phenomena of synergy, addition, indifference and antagonism, and also that of domination of an antibiotic in the association. This one can work, by example, by imposing its bactericidal's speed (vancomycin) or by selecting deficient surviving bacteria (rifampicin). This, the intrinsic and sometimes undesirable characteristics of some antibiotics are not masked by the others antibiotics used in the association. This mechanism must be proved in vivo, but it is sure that during physico-chemical inactivity or during diffusion's deficiency of one of antibiotics, transient relation of concentrations are favorable conditions for domination's expression.