Behavior of Escherichia coli O157:H7 in Leafy Vegetables

Abstract

Leafy vegetables, including lettuce and spinach, have been implicated in several outbreaks of foodborne disease caused by Escherichia coli O157:H7, a pathogen of increasing public health significance because of the severity of the gastrointestinal illness and long-term, chronic sequelae that can result from infection. A definitive association between the consumption of leafy vegetables and human disease provides implicit evidence of transfer from animal sources to field crops and retail commodities, including minimally processed or fresh-cut products. Understanding the behavior of E. coli O157:H7 in leafy vegetables during production, after harvest, in storage, during processing, and in packaged fresh-cut products is essential for the development of effective control measures. To this end, previous research on the fate of the species at each step in the production of market-ready leafy vegetables is reviewed in this study. Several critical gaps in knowledge are identified, notably uncertainty about the location of contaminating cells on or in plant tissues, behavior in packaged products stored at low temperatures, and the influence of environmental stresses on growth and infectivity.

Internalization of Salmonella enterica in Leaves Is Induced by Light and Involves Chemotaxis and Penetration through Open Stomata

“…This report is in agreement with the notion that infiltration of foodborne pathogens through stomata was considered a passive event (9,14,35). It was recently reported that vacuum cooling results in increased infiltration of E. coli O157:H7 into romaine lettuce tissue.…”

“…Upon introduction to the leaf surface, both plant-and foodborne pathogens encounter multiple stresses, such as limited nutrients, UV irradiation, and desiccation (4,9,14,22,35). Although penetration of plant pathogens into leaf tissue was considered a passive mechanism (9,14,35), recent studies suggest that stomata play an active role in controlling internalization of both human and plant pathogens as part of the plant's innate immune system (24,35).…”

“…Although penetration of plant pathogens into leaf tissue was considered a passive mechanism (9,14,35), recent studies suggest that stomata play an active role in controlling internalization of both human and plant pathogens as part of the plant's innate immune system (24,35). Several plant pathogens were shown to exploit stomatal openings to gain entry into internal leaf compartments, which provide them with a more favorable environment (24,35).…”

Escherichia coli Common Pilus (ECP) Targets Arabinosyl Residues in Plant Cell Walls to Mediate Adhesion to Fresh Produce Plants

“…coli O157:H7, one of the most important causative agents of fresh produce-associated outbreaks, is often linked with contaminated lettuce and spinach (11,12).…”

Leaf Age as a Risk Factor in Contamination of Lettuce withEscherichia coliO157:H7 andSalmonella enterica

“…However, studies performed with whole-cell bacterial biosensors for sucrose and fructose revealed heterogeneous distribution of these sugars on leaf surfaces, with few microsites harboring abundant quantities of them (8,22,28). In addition, rapid changes in water availability on the leaf surfaces of crops affect the solubility of nutrients that may be used by the plant microflora (15).…”