The antibiotic ceftriaxone was conjugated to Ag and Au nanoparticles. The activity of the conjugates against Escherichia coli ATCC 8739 was compared to that of pure ceftriaxone and of unconjugated nanoparticles using atomic force microscopy and more conventional techniques such as the agar well diffusion method. Conjugation to Ag nanoparticles increased the antibacterial activity of ceftriaxone by about 2 times, and conjugation to Au by about 6 times. Conjugation also appeared to improve the kinetics of the antibiotic. Thus, for example, membrane damage was barely evident two hours after contacting a cell culture with pure ceftriaxone. In the same time, Ag conjugates severely damaged membranes and Au conjugates completely disrupted the cell morphology.