Enhancing Understanding of Bacterial Pathogens in Fresh Produce and Dairy Supply Chains: Insights Into Population Dynamics, Sanitizer Tolerance, Persistence, and Transmission

Abstract

Identifying strategies that can control the bacterial foodborne pathogens Listeria monocytogenes, Salmonella enterica, and pathogenic Escherichia coli in fresh produce and dairy products remains a top priority in food safety. Importantly, these control strategies need to be both (i) deemed appropriate based on scientific evidence and (ii) practical to implement. In this collection of works, we aimed to use science-based evidence to enhance our understanding of the risks associated with these bacterial pathogens in fresh produce and dairy supply chains, and identify strategies that can be practically applied to control their presence and proliferation in associated food products.

A scoping review was conducted to summarize the current literature that investigates population dynamics of pathogenic and non-pathogenic E. coli, Listeria spp., and Salmonella spp. on whole fresh produce. Several key knowledge gaps were identified, highlighting areas where more research is needed to support the establishment of time-dependent metrics for controlling these bacterial pathogens on fresh produce. Subsequent works focused specifically on characterizing risks associated with Listeria in food processing environments, given the severity of disease outcomes associated with L. monocytogenes infections, and the notorious number of listeriosis outbreaks that have been historically traced back to cross-contamination of food products from the processing environment. Key topics explored here included (i) assessing the ability of Listeria to acquire tolerance to sanitizers that are commercially-relevant for food processing environment sanitation, (ii) evaluating the effectiveness of using simplified environmental sampling strategies towards improving Listeria control in small- and medium-sized dairy processing facilities, and (iii) characterizing Listeria contamination patterns in a farmstead dairy processing facility and its associated dairy farm environment. In each of these works, both classical culture-based and molecular tools (e.g., whole genome sequencing) were leveraged to yield more in-depth insights about Listeria sanitizer tolerance, persistence, and transmission in food processing environments. Overall, these works provide important insights that can be used to support the development of strategies that minimize the contamination and proliferation of fresh produce and dairy products with high-risk bacterial pathogens.