Background: The green synthesis of cadmium sulfide (CdS) nanoparticles has been regarded as the most promising technique for their prospective applications in biological system. Aim of the work: In this study isolation of different bacterial strains from stool samples of healthy volunteer, selection of the most efficient bacterial strains able to reduce cadmium sulfide metal into nanoparticles. Characterization of biosynthesized metal nanoparticles by standard analytical methods. Mediating the biosynthesized cadmium sulfide nanoparticles in medical applications in comparison to those produced by chemical methods. Materials and methods: Extracellular Escherichia coli E-30 and Klebsiella pneumoniae K-6 isolated from stool samples were the strains used for biosynthesis. Cadmium sulfide nanoparticles were also produced by wet chemical method. The characterizations of cadmium sulfide nanoparticles were done by using UV-Visible Spectroscopy, Transmission electron microscopy (TEM), energy   dispersive   x-ray (EDX) and Fourier transform infrared spectroscopy (FT-IR). Results: Escherichia coli E-30 has shown to be efficient in synthesizing cadmium sulfide nanoparticles where CdS nanoparticles were with average size ranging from 3.2 to 44.9 nm while average size of CdS nanoparticle was synthesized by Klebsiella pneumoniae K-6 ranging from 8.5 to 44.9 nm. While cadmium sulfide nanoparticles synthesized by wet chemical method, ranging from 8.77 to 16.50 nm. Biosynthesized cadmium sulfide nanoparticles by Escherichia coli E-30 showed highest antimicrobial activity on Aspergillus fumigatus, Geotricum candidum, Bacillus subtilis,Staphylococcus aureus and Escherichia coli than chemical synthesized of CdS nanoparticles. Conclusion: Escherichia coli and Klebsiella pneumoniae isolated from stool samples had the ability to produce cadmium sulfide nanoparticles. This kind of microorganisms can be used for synthesis of nanoparticles and heavy metal absorption for detoxification of environment.