Whole-Genome Sequencing Analysis of Listeria monocytogenes from Rural, Urban, and Farm Environments in Norway: Genetic Diversity, Persistence, and Relation to Clinical and Food Isolates

Abstract

Listeria monocytogenes is a deadly foodborne pathogen that is widespread in the environment. For effective management, both public health authorities and food producers need reliable tools for source tracking, surveillance, and risk assessment.

Pervasive Listeria monocytogenes Is Common in the Norwegian Food System and Is Associated with Increased Prevalence of Stress Survival and Resistance Determinants

“…Cross-contamination of food products with L. monocytogenes during processing is a major concern, especially with regard to ready-to-eat (RTE) products that support growth of the pathogen prior to consumption. Since the pathogen is widespread in natural and urban environments ( 1 , 2 ) and able to form biofilms and withstand various stresses such as disinfection agents, high and low pH, and low temperatures ( 3 , 4 ), it is very difficult to eliminate from food processing environments. Clonal populations of L. monocytogenes that survive in the processing environment over an extended time-period (months or years) are referred to as persistent L. monocytogenes ( 5 , 6 ).…”

“…There is a consensus that certain L. monocytogenes strains are more frequently isolated from food processing factories because of their increased ability to survive and multiply in niches that are difficult to keep clean ( 2 , 7 , 28 , 46 ). However, there is no consensus on the operational definition of a persistent strain in terms of the number of independent isolation events or the time frame ( 7 , 28 ).…”

“…This may occur due to contamination from a common source of raw materials or preprocessed product (e.g., slaughtered salmon) or through transfer of used processing equipment between food processing plants. In addition, evidence suggests that highly similar L. monocytogenes strains may be present in apparently unassociated locations, at least in natural environments ( 2 ). However, there is limited knowledge regarding the extent to which highly similar genetic clones disseminate or pervade and establish in multiple separate locations.…”

Occurrence of Fecal Bacteria and Zoonotic Pathogens in Different Water Bodies: Supporting Water Quality Management

“…and L. monocytogenes [16,17], but these have also been isolated from other water sources, such as rivers and other fresh water sources [17][18][19]. Their presence is also more frequently associated with urban settings when compared to rural or pristine environments [20,21].…”

“…While there are extensive studies on the distribution of L. monocytogenes and Salmonella spp. in humans, animals, foods and food-processing environments [21][22][23], limited data is available regarding the distribution of these species in the general environment. A better understanding of the pathogen dynamics associated with different water ecosystems is indispensable for the development of effective strategies to mitigate the risk of human disease.…”