Nanocomposites of polymethyl-methacrylate (PMMA) have gained high attention owing to their extensive applications as antibacterial agents. The antibacterial activities of Ag and TiO 2 nanoparticles are well established. This study intended to differentiate the antibacterial activities exhibited by PMMA/TiO 2 /Ag nanocomposite, towards bacterial consortium and single dominant bacterial isolates from packaged drinking water. A silver nanoparticle dose-dependent decline in cell viability of consortium and individual isolates was compared under UVC and dark conditions to evaluate the antibacterial activity of the nanocomposite. To corroborate with the viability results, oxidative stress & cell permeability was also assessed under similar conditions. Surface characterization of PMMA/TiO 2 /Ag nanocomposite was performed by FTIR, AFM, and SEM analyses after interaction with the bacteria. The PMMA/TiO 2 /Ag nanocomposite showed enhanced antibacterial activity against single bacterial isolate compared to the consortium. The outcomes from the study with PMMA/TiO 2 /Ag nanocomposite necessitate relooking at the test design for assessment of antibacterial effects in real conditions incorporating the impact on the consortium of microorganisms instead of individual strains.