Nanoparticles biosynthesis and its applications is a rapidly developing field. The biological silver nanoparticles (AgNPs) are being used as inhibitory and antimicrobial agents. In the current investigation, synthesis of silver nanoparticles by bacterial strain isolated from soil sample contaminated with crude petroleum oil was studied. Molecular identification of the bacterial isolate showed it as a strain of Sphingobacterium mizutaii. The biosynthesized nanoparticles characterized by the UV-Vis spectroscopy which exhibited a broad absorption spectrum band around 420 nm. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis confirmed the formation of varying size silver particles in the range from 4.5-31.6 nm. The Interaction between silver nanoparticles and proteins were characterized by Fourier transform infrared (FTIR) spectroscopy. The combination effects of AgNPs with the antiseptic agent (Dettol) was then studied. The antimicrobial effect of AgNPs- Dettol combination increased significantely in case of E. coli, K. pneumoniae, B. subtilis and Candida krusei.