Hyperspectral Reflectance Imaging for Detecting a Foodborne Pathogen: Campylobacter

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This article is concerned with the development of a hyperspectral reflectance imaging technique for detecting and identifying one of the most common foodborne pathogens, Campylobacter. Direct plating using agars is an effective tool for laboratory tests and analyses of microorganisms. The morphology (size, growth pattern, color, etc.) of colonies grown on agar plates has been widely used to tentatively differentiate organisms. However, it is sometimes difficult to differentiate target organisms like Campylobacters from other contaminants grown together on the same agar plates. A hyperspectral reflectance imaging system operating at the visible and near-infrared (VNIR) spectral region from 400 nm to 900 nm was set up to measure spectral signatures of 17 different Campylobacter and non-Campylobacter subspecies. Protocols for culturing, imaging samples and for calibrating measured data were developed. The VNIR spectral library of all 17 organisms commonly encountered in poultry was established from calibrated hyperspectral reflectance images. A pattern classification algorithm was developed to locate and identify 48 h cultures of Campylobacter and non-Campylobacter contaminants on background agars (blood agar and Campy-Cefex) with over 99% accuracy. The Bhattacharyya distance, a statistical separability measure, was used to predict the performance of the pattern classification algorithm at a few wavelength bands chosen by the principal component analysis (PCA) band weightings. This research has a potential to be expanded to detect other pathogens grown on agar media.