The goal of this proposed work is to develop a rapid, automated, multi-analyte diagnostic system based on a novel microflow cytometer for screening exposure to category B pathogens. The resulting device will be portable and field deployable for rapid point-of-care and on-site diagnosis of exposure. The technology can also be used for monitoring efficacy of vaccines as they are developed. Target analytes will include, but are not limited to, Brucella, Coxiella, Salmonella, Campylobacter, E. coli, Shigella, Listeria, Cryptosporidium parvum, Giardia lamblia, and VEE. Development of the proposed diagnostic system will be two pronged, including both assay and device development. First;potential assay formats, using coded microspheres as the solid support, will be investigated, including direct detection of pathogen and indirect identification of pathogen exposure by detecting anti-pathogen antibodies. Optimized assays will be run both in buffer and spiked clinical samples. Candidate capture and tracer reagents, including antibody and non-antibody recognition molecules, will be screened with the goal of reaching physiologically relevant limits-of-detection. Magnetic nanoparticles will be used to pre-concentrate pathogens within the disposable element of the device. Second, expansion of the current microflow cytometry technology will include development and optimization of the 3-color analysis capabilities, automation of the portable system, and inclusion of pathogen sorting capability. The developed system can address of number of the areas of concern for public health including: Assays that demonstrate the highest performance for their detecting pathogens in relevant clinical samples (e.g., sensitivity, specificity, rapidity, ruggedness, ease-of-use and cost-effectiveness). Rapid sample preparation, processing, and target concentration. Improved technologies, methodologies, and reagents for simultaneous testing for multiple targets. Technologies that integrate multiple methods of parallel measurements for detection in the same platform, such as identifying nucleic acids, proteins, and other targets from agents in the same assay. Technologies targeting multiple biomarkers or signature profiles to identify human immune or other physiological responses during infection. Technology adaptable for high throughput, robotic, and automated data output and analyses at minimal cost.