The antimicrobial polymer/polymer macrocomplexes were synthesized by radical alternating copolymerization of N-vinyl-2-pyrrolidone with maleic anhydride [poly(VP-alt-MA)] with 2,2'-azobis-isobutyronitrile as an initiator at 65 degrees C in dioxane solutions under nitrogen atmosphere, and interaction of prepared copolymer with poly(ethylene imine) (PEI) in aqueous solutions. The susceptibility of some Gram-negative (Salmonella enteritidis and Escherichia coli) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria to the alternating copolymer and its PEI macrocomplexes with different compositions in microbiological medium was studied using pour-plate technique. All the studied polymers, containing biologically active moieties in the form of ionized cyclic amide, and macrobranched aliphatic amine groups and acid/amine complexed fragments, were more effective against L. monocytogenes than those for Gram-positive S. aureus bacterium. This fact was explained by different surface layer structural architectures of biomacromolecules of tested bacteria. The resulting polymeric antimicrobial materials are expected to be used in various areas of medicine and food industry. (c) 2006 Wiley Periodicals, Inc.