Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2009
Publication Date: 4/28/2009
Citation: Yoon, S.C., Lawrence, K.C., Siragusa, G.R., Line, J.E., Park, B., Feldner, P.W. 2009. Hyperspectral Reflectance Imaging for Detecting a Foodborne Pathogen: Campylobacter. Transactions of the ASABE. 52(2): 651-662
Interpretive Summary: Campylobacter commonly found in poultry or cattle is the leading foodborne pathogen causing diarrhea illness in the US and worldwide. Detection and identification of Campylobacters obtained from food samples like chickens involve time-consuming or complicated laboratory tests such as culturing on agar plates and genetic tests. Direct culturing on agar plates has been known as an effective method to isolate and enumerate Campylobacters; however, distinguishing Campylobacters from non-Campylobacter contaminants that frequently grow on many existing agars is difficult. The objective of this research was to develop an imaging technology for detecting and identifying cultures of Campylobacters and non-Campylobacters grown on Petri dishes of agar media by using a hyperspectral imaging spectrometer. A spectral library was established from the microorganism colonies (Campylobacters, non-Campylobacters and agar media) and exploited for classifying the colonies. One spectral band at 501 nm for Campy-Cefex or at 503 nm for blood agar was found to be important to separate the tested microorganisms with over 99% accuracy. The fully developed imaging system is expected to automatically locate and identify Campylobacters grown on Petri dishes and has a potential to be expanded to detect other pathogens like E-coli and Salmonella grown on agar media.
Technical Abstract: This paper 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 48h cultures of Campylobacters 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.