In this paper we show that preparation of Ag doped hydroxyapatite by an adapted co-precipitation method at 100°C has several advantages over other techniques. Specifically, it can generate highly crystalline nanopowder Ag:HAp which could be used for implantable medical devices. The XRD of HAp (xAg = 0) and Ag:HAp (xAg = 0.05, and xAg = 0.4) also demonstrates that powders obtained by co-precipitation at 1000C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The SEM results suggested that Ag+ doping had little influence on the morphology and dimension of the samples. It can be seen that all the samples consist of elipsoidal particles. The antibactericidal activity of Ag:HAp-NPs with xAg = 0, xAg = 0.05, and xAg = 0.4 on Bacilus and E.coli ESBL 1576 were presented. The Ag:HAp-NPs with xAg = 0.05, and xAg = 0.4 inhibited the biofilm development both by the gram-positive (Staphylococcus aureus 0364) and the gram-negative (Providencia stuartii 1116) strains. On the other hand, our studies have shown that Ag:HAp with xAg = 0 had no antibacterial activity against gram-positive and gram-negative bacteria