Silver-loaded zirconium phosphate (AgZ) was combined with hydroxyapatite (HA) to prepare an antibacterial composite (AgZ/HA) with improved activity in the presence of Cl-. When Escherichia coli cells were deactivated in 154 mM NaCl, the bacterial survival ratio at 90 min for AgZ/HA was 3.9 x 10(-4) compared to 1.2 x 10(-1) for AgZ itself. Because the bactericidal activity of AgZ/HA decreased with increasing phosphate ion up to 10 mM, cell adsorption onto the combined HA moiety probably compensated for the Cl- -induced deterioration in the activity of the silver-based bactericide.