Roles of a Novel Crp/Fnr Family Transcription Factor Lmo0753 in Soil Survival, Biofilm Production and Surface Attachment to Fresh Produce of Listeria monocytogenes

Abstract

Listeria monocytogenes is a foodborne bacterial pathogen and the causative agent of an infectious disease, listeriosis. L. monocytogenes is ubiquitous in nature and has the ability to persist in food processing environments for extended periods of time by forming biofilms and resisting industrial sanitization. Human listeriosis outbreaks are commonly linked to contaminated dairy products, ready-to-eat meats, and in recent years, fresh produce such as lettuce and cantaloupes. We identified a putative Crp/Fnr family transcription factor Lmo0753 that is highly specific to human-associated genetic lineages of L. monocytogenes. Lmo0753 possesses two conserved functional domains similar to the major virulence regulator PrfA in L. monocytogenes. To determine if Lmo0753 is involved in environmental persistence-related mechanisms, we compared lmo0753 deletion mutants with respective wild type and complementation mutants of two fully sequenced L. monocytogenes genetic lineage II strains 10403S and EGDe for the relative ability of growth under different nutrient availability and temperatures, soil survival, biofilm productivity and attachment to select fresh produce surfaces including romaine lettuce leaves and cantaloupe rinds. Our results collectively suggested that Lmo0753 plays an important role in L. monocytogenes biofilm production and attachment to fresh produce, which may contribute to the environmental persistence and recent emergence of this pathogen in human listeriosis outbreaks linked to fresh produce.

Transfer of Pathogens from Cantaloupe Rind to Preparation Surfaces and Edible Tissue as a Function of Cutting Method

“…We noted limited differences in adherence among the different strains from the 2011 cantaloupe outbreak; similar adherence potentials were observed with other strains examined here and by others (1,22,28). Furthermore, the extent of growth did not differ significantly among the Table 1.…”

Sources and survival ofListeria monocytogeneson fresh, leafy produce

“…Biofilm production and the ability of L. monocytogenes to survive in soil appear to be intimately linked as mutants which lack Lmo0753 (a prfA like transcription factor gene) form poor biofilms and show poor survival in soil compared to wild‐type strains (Salazar et al . ). Furthermore, Lmo0753 is highly conserved in lineage I and II strains, which are more commonly isolated from the soil than lineage III and IV strains (Locatelli et al .…”

“…Interestingly, agrA and agrD deletion mutants have altered ability to adhere to surfaces, suggesting the agr system's involvement in the early stages of biofilm formation (Rieu et al 2007). Biofilm production and the ability of L. monocytogenes to survive in soil appear to be intimately linked as mutants which lack Lmo0753 (a prfA like transcription factor gene) form poor biofilms and show poor survival in soil compared to wild-type strains (Salazar et al 2013). Furthermore, Lmo0753 is highly conserved in lineage I and II strains, which are more commonly isolated from the soil than lineage III and IV strains (Locatelli et al 2013a;Linke et al 2014).…”

Listeria monocytogenes in Fresh Produce: Outbreaks, Prevalence and Contamination Levels

“…That is, the organism usually infects sterile parts of the body, such as the liver [34], spleen [35], cerebral spinal fluid [36] and blood [37]. In healthy adults, diarrhea and fever are the main symptoms [38], in pregnant women it is fever, diarrhea, abortion or stillbirth [39], and in the newborn it can cause sepsis, pneumonia and meningitis [40,41,42,43,44]. L. monocytogenes can also cause a non-invasive disease, usually as a febrile gastroenteritis or non-invasive gastroenteritis, and it has been linked to outbreaks resulting from contaminated deli meat [45,46], chocolate milk [47], cheese [48,49,50], smoked fish [51,52] and corn [13].…”