Surface reactions were performed on polypropylene (PP) surfaces to retard the simultaneous growth of Staphylococcus aureus (S. aureus) and Pseudomonas putida (P. putida) bacteria. Microwave plasma reactions in the presence of maleic anhydride (MA) resulted in the formation of acid groups on the surface of PP. Such surfaces were further modified by conducting two parallel reactions: (1) poly(ethylene glycol) (PEG) was attached to COOH groups of the PP surface, followed by penicillin V (PEN) reactions to target S. aureus destruction and (2) diglycidyl PEG was attached, followed by gentamicin (GEN) reactions, to create antimicrobial surfaces targeted at A putida. Simultaneous gram "+" and gram "-" resistance was obtained by varying the PEN/GEN ratios on such modified PP surfaces, thus providing the controllable degree of gram "+" and gram "-" antimicrobial strength. While spectroscopic analyses revealed chemical attachments of PEN and GEN, the effectiveness against proliferation of S. aureus (Gram +) and P. putida (Gram -) bacteria was determined using liquid culture tests. These studies show for the first time the formation of tunable antimicrobial polypropylene surfaces with controllable strength.