Magnetic nanoparticles with a few nanometers to micrometer diameter are largely used in biomedical application such as diagnosis, drug delivery, and treatment of numerous pathogens because of its biocompatibility and inertness. In the present investigation we are interested in synthesis of core shell magnetic nanoparticle in order to attach various biomolecules and bioconjugation. Here the silver coated magnetic nanoparticle is of our choice of nanoparticles in which they can be further derivative with biomolecules and drugs so that they can be further used in imaging and preconcentration of pathogenic microorganism in dilute concentration. Synthesis of these nanoparticles can be achieved by co-precipitation method or by thermolysis of iron oleate with different experimental condition followed by reaction with respective metal salt in order to synthesis of core shell system. The reactivity of core shell magnetic nanoparticles with fluoroquinolone antibiotics has been tested and their combined system can be utilized to study the Antimicrobial actions of drugs protected nanoparticles. The drugs protected core shell nanoparticles shows enhanced antimicrobial action against various microorganisms than the pure drug. This method can be further extended for the preconcentration of microorganism from drinking water samples. The proposed method is found to be easier way detection of microorganism at low level concentration.