Due to rampant misuse of antibiotics, certain bacterial organisms have developed resistance against them as a result of genetic modifications, rendering a lot of the traditionally used antibiotics ineffective. Thus, introduction of a new class of antibacterial materials is paramount. This article reports exploring the comparative performances of monometallic Au, bimetallic AuPt and trimetallic AuPtCu as potential antibacterial agents for the future. The materials were obtained as nanofluids via a one-pot microwave synthesis procedure and subsequently were subjected to characterization by high-resolution electron microscopy, dynamic light scattering, X-ray diffraction, absorption spectroscopy and X-ray photoelectron spectroscopy, etc. It was found that the multimetallic particles were composed of several bimetallic alloy nano-islands and with increasing number of components the particle size became smaller and the microstructure became littered with defects. This had a profound effect on the antibacterial activity as the trimetallic AuPtCu was found to be the most effective against both the gram-negative and gram-positive bacterial strains. A detailed rationalization for the same has been provided based on the analysis of the structure-property-activity correlation. We anticipate the findings to be really important going forward; in the research and fabrication of new age medicines against drug-resistant micro-organisms.