P128 Dose Response. Biological activity of P128 at different protein concentrations was correlated with varied target cell numbers. P128 in the range 0.25 μg/ml – 10 μg/ml was added to S. aureus cells taken in the range of 5×101 – 5×108 cells/ml. Bactericidal activity was assessed by the CFU-reduction assay. This was evaluated in duplicates and the experiment performed twice. Results are expressed as mean residual CFU/ml±standard deviation.