2011 Annual Report
Once reasonable results are obtained for pure cultures, important food matrices will be spiked with pathogens and bio-threat agents at varying concentration levels and hyperspectral images will be collected on both the total contaminated food matrices and on a rinsate from the infected food matrices. Multivariate calibration models, based on the spectral libraries of the bio-threat agents and food matrices, will then be developed and the lower limit of detection for each pathogen and bio-threat agent will be determined.
A visible and near-infrared (VNIR) hyperspectral imaging technique was developed to detect and differentiate Campylobacter in Petri dishes from five primary contaminants commonly found in commercial poultry carcass rinses. A protocol for imaging the spots of bacteria growing in agar media and processing their hyperspectral images was developed such that spectral libraries of the pure bacteria were collected for development of classification and validation models. From the research based on spot-plate imaging, the research was extended to image spread plates using the known mixture formula of pure bacteria. Currently, the protocol for imaging spread plates of pure pathogenic bacteria has been established and the performance of detection is being validated with results obtained by phase contrast microscopic tests.
A short-wavelength infrared (SWIR) hyperspectral imaging system was developed to image Petri dishes in the wavelength range from 1,000 to 2,500 nanometers (nm). The developed SWIR hyperspectral imaging system was designed to extract spectral fingerprints beyond the wavelength range most commonly used for hyperspectral imaging (400 to 1000 nm). The SWIR imaging system contains a Mercury Cadmium Telluride (MCT) camera with a spectrograph, a moving stage with precision motion and location control, a sample holder, and custom application software for image acquisition via motion and camera controls. The system is also capable of imaging a Petri dish either in the reflectance or transmittance mode. Next, the potential of the system for detection of pathogens in agar media was investigated by conducting a study with a spectrometer and the SWIR imaging system. The study found the spectral region from 1,000 to 2,500 nm was not viable for detecting pathogen colonies on agar plates because the water in the agar media dominated the spectral responses.