The present invention provides compositions and methods for reducing bacterial contamination or infection in plants, animals, fabrics, and products therefrom. The present invention also provides compositions and methods for reducing human infections and the emergence of antibiotic resistance. In particular, the invention provides magnetic nanoparticles comprising bactericidal or bacteriostatic enzymes in one component, substrates for the enzymes in a second component, and a bactericidal chemical agent that works in combination or synergistically with the enzymes. The compositions are dormant and become active upon exposure to hydration, oxygen, or mixing.