The progressive growth of bacterial resistance to antibiotic drugs requires the creation of highly efficient nanomaterials. Aluminum oxide is a stable non-toxic semiconductor material; however, the photocatalytic properties of its modifications in relation to microorganisms are not well understood. In this study, we used new 3D composites of aluminum oxyhydroxide (Al2O3 × nH2O) in three modifications (γ, α and θ), which are a mesh of 150 nm nanofibrils. The assessment of the photocatalytic antibacterial properties of the composites was carried out on the museum strain S. aureus 209 P.