new therapeutic methods and compositions are provided for treating against an infectious agent in a mammal by administration of a polymeric material having linked thereto a plurality of therapeutic agents against the infective agent , wherein the polymer comprises polymerized dextran or ethylene glycol units . the compositions and methods of the invention are particularly useful to treat against bacterial infections , including treatment of mammalian cells infected with gram - negative bacteria or gram - positive bacteria . the compositions of the invention can be useful for treating against anthrax , staphylococcus , pneumococcus and other bacteria , parasites , fungi , viral and protozoan infections .