The antimicrobial properties of bacterial synthesized silver nanoparticles of Bacillus subtilis and Escherichia coli origin were tested against five isolates namely: Pseudomonas sp, Bacillus sp, Salomonella sp, Shigella sp and Escherichia coli. The silver nanoparticles were synthesized from 10 Mm of AgNO3 and the bacterial culture supernatant. Optimum physiological conditions of bacterial nanoparticles’ synthesis were determined using the Box behnken design with three factors and three levels which include pH (6, 7, 8), time (24, 48, 72hrs) and temperature (25, 30, 32°C). The different significance of the physiological factors was determined. The optimal conditions for the synthesis of silver nanoparticles were determined as pH 6.9, Temp. 25°C and Time 72 hrs for Escherichia colinanoparticles(ENP) and pH 7.79, Temp. 25oC and Time of 72 hrs for Bacillus subtilis nanoparticles (BNP). The antimicrobial activity of the microbial synthesized silver nanoparticles was determined using the kill kinetics and the Kirby bauer well-in-agar diffusion method. ENP had better activity than BNP on Shigellasp, while the reverse was the case when tested against Salmonella sp. Time kill kinetics shows that BNP and ENP inhibited the growth of Salmonellasp, Pseudomonas sp, Bacillus sp, Shigella sp and E. coli at 12 hrs and 20 hrs, 28 hrs and 32 hrs, 36 hrs and 32 hrs, 24 hrs and 16 hrs and 32 hrs and 16 hrs respectively. All nanoparticles recorded lower activity than the control drug, Ciprofloxacin.