Modification of the rheological properties of cellulose acetate phthalate in 2-methoxyethanol/acetone/water, at different compositions of solvent mixtures, allowed the identification of optimal composition of solvent mixtures for obtaining fibers with controlled diameters. Changing the solvent content in the casting solutions favors modification of the morphological aspects of cellulose acetate phthalate (CAP) films, as observed from atomic force microscopy images. Silver nitrate was incorporated into CAP, as a dispersion medium, and the silver-containing polymer (Ag-CAP) films thus obtained were studied for obtaining information on antimicrobial activity, using Escherichia coli ATCC 10536 and Staphylococcus aureus ATCCC 6538 microorganisms. The results were compared with the antibacterial activity of nano-silver-containing cellulose acetate (Ag-CA) films. The different inhibiting effects of CA or Ag-CA and of CAP or Ag-CAP on the tested Escherichia coli and Staphylococcus aureus bacteria are due to a different antimicrobial activity of the polymers and to the antiseptic character of nano-silver.