Attachment of Listeria monocytogenes to Radish Tissue Is Dependent upon Temperature and Flagellar Motility

Abstract

Outbreaks of listeriosis and febrile gastroenteritis have been linked to produce contamination by Listeria monocytogenes. In order to begin to understand the physiology of the organism in a produce habitat, the ability of L. monocytogenes to attach to freshly cut radish tissue was examined. All strains tested had the capacity to attach sufficiently well such that they could not be removed during washing of the radish slices. A screen was developed to identify Tn917-LTV3 mutants that were defective in attachment to radish tissue, and three were characterized. Two of the three mutations were in genes with unknown functions. Both of the unknown genes mapped to a region predicted to contain genes necessary for flagellar export; however, only one of the two insertions caused a motility defect. The third insertion was found to be in an operon encoding a phosphoenolpyruvate-sugar phosphotransferase system. All three mutants were defective in attachment when tested at 30°C; the motility mutant had the most severe phenotype. However, not all of the mutants were defective when tested at other temperatures. These results indicate that L. monocytogenes may use different attachment factors at different temperatures and that temperature should be considered an important variable in studies of the molecular mechanisms of Listeria fitness in complex environments.Listeria monocytogenes is a gram-positive pathogen that causes a multitude of symptoms, including septicemia, abortion, liver failure, and meningitis (50). When L. monocytogenes is not living as an intracellular invader, it can be isolated from the feces of animals as well as humans and from the soil, where it can survive as a saprophyte for 10 to 12 years. From these locations, it can contaminate the food supply in many ways. It can survive in sewage and enter the soil, where it may become associated with plants and/or farm animals before entering food-processing plants, grocery stores, and home refrigerators (2, 10). In all of these niches, L. monocytogenes can survive and even thrive, leading to contamination of foods and ingestion of the pathogen. L. monocytogenes is quite hardy under a variety of environmental stresses. It has been reported that it can grow at temperatures of between Ϫ0.4 and 50°C and withstand extremes of osmotic pressure, as evidenced by growth in 10% NaCl, and it displays a pH range of 4.3 to 9 (18, 21).While food contamination with L. monocytogenes is most often associated with smoked meats and dairy products, fresh produce has also been implicated in outbreaks and sporadic cases of listeriosis. Specific produce-related outbreaks of listeriosis and febrile gastroenteritis caused by L. monocytogenes have been associated with contaminated cabbage, corn, and lettuce and/or celery (8,30,51). In addition, this organism has caused the recall of vegetables, including red peppers, sprouts, and lettuce, and potato salad (4-7, 13). L. monocytogenes has been isolated from radishes, potatoes, cucumbers, and cabbage in surveys of produce from U.S. grocery s...

Flagellin fromListeria monocytogenesIs Glycosylated with β-O-LinkedN-Acetylglucosamine

“…Flagella have been shown to be important in the initial attachment of the organism to various surfaces at temperatures of less than 30°C (13,47). Flagellar glycosylation may have an important role in environmental interactions particularly within the food processing environment, where temperatures are generally maintained at much lower than ambient levels, which are optimal for the production of flagella.…”

“…The molecular mechanisms governing both attachment and biofilm formation have yet to be studied in detail. However, the flagella of L. monocytogenes have been shown to be involved in the attachment of the organism at temperatures below 30°C to both stainless steel (47) and plant tissues (13).…”

Listeria monocytogenes Biofilm-Associated Protein (BapL) May Contribute to Surface Attachment of L. monocytogenes but Is Absent from Many Field Isolates

“…The factors required for biofilm formation in L. monocytogenes are still relatively unknown, although some progress has been made in this area through the screening of insertion mutant libraries (19,39) and proteomic studies (21,40). Several genes have been identified, including relA that encodes (p)ppGpp synthetase (39), the superoxide dismutase gene (sod), and the gene encoding 30s ribosomal protein S2 (rpsB) (40), but because these do not code for surface proteins, they will not directly determine attachment.…”

Previously uncharacterized Salmonella enterica genes required for swarming play a role in seedling colonization

“…Salmonellosis accounts for more than half of foodborne disease outbreaks, and the most common food commodity to which outbreak-related cases were attributed was produce (CDC, 2009). Instead of this being due to incidental contamination, the animal pathogens Salmonella enterica, Escherichia coli and Listeria monocytogenes utilize specific molecular mechanisms to attach to and then colonize plant seedlings and tissues (Gorski et al, 2003;Jeter & Matthysse, 2005). S. enterica, in particular, appears to employ an arsenal of surface molecules for attachment and colonization.…”