RAPID DETECTION OF VIABLE BACTERIA IN AGRICULTURAL WASH WATERS – A DROPLET-BASED APPROACH
Harmon, James Brian
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Foodborne illness is a significant public health concern worldwide, with a global burden of disease comparable to HIV/AIDS, malaria and tuberculosis. The World Health Organization estimated there were approximately 2 billion cases and over 1 million deaths associated with foodborne illness in 2010. In the United States (U.S.) alone, foodborne contamination and associated illness is responsible for an estimated 48 million cases per year, with total health-related costs estimated between $51 and $76.1 billion annually. From 1998 to 2008, nearly half of all foodborne illnesses in U.S. were attributable to produce and over 20% were attributable to leafy greens. The food industry must continually evaluate critical control measures for its most vulnerable crops, improve upon detection methods, and maintain collaborative relationships with surveillance networks to lessen prevalence and severity of foodborne outbreaks. The food industry utilizes hazards analysis and critical control point (HACCP) programs to identify and mitigate vulnerabilities in the farm-to-consumer route. Wash waters are essential for removing debris and sanitizing produce before rapidly shipping to the end consumer. If sanitization efficacy is compromised, wash waters can cross-contaminate large batches of previously uncontaminated produce. For this reason, fresh-cut produce wash waters are a critical control point in industrial produce processing facilities. This dissertation assesses inhibition challenges wash waters present to qPCR and a means to overcome these challenges by using common chlorine quenchers. Droplet-based microfluidics, paired with activated fluorescence, is evaluated as a rapid alternative to detect viable bacterial contamination. The droplet-based method, paired with a FITC-conjugated antibody, achieved excellent sensitivity and specificity for the target bacteria – artificially spiked Salmonella – in a produce wash water acquired from a major Mid-Atlantic produce processing facility. Most importantly, viable bacterial detection was achieved in less than five hours – dramatically reducing time needed for traditional culturing that can take days. In-droplet microfluidics shows great promise for preventing produce-associated foodborne outbreaks by potentially providing food industry HACCP program managers a same-day (or same-shift) detection capability.