Recent studies of human pathogens in produce models have suggested that foodborne pathogens, many of which are Gram-negative, may interact with plants by mechanisms evolutionarily conserved, and at least somewhat similar to those described above for plant bacteria (Table 2.3). Studies of human pathogens and produce have involved, generally, assessments of the attachment and survival of human pathogens on postharvest, retail market products [121-126]. Other studies have used human pathogen-plant models to investigate attachment on seeds and seedlings or young plants that are contaminated in the laboratory and grown in chambers under various conditions (e.g., humidity, light, temperature, competitors) [27,127-129]. The biology of attachment of human pathogens in preharvest (soil, other microbes, temperature, UV, extended exposure time) and postharvest (rinse water, shorter exposure time, temperature) environments may be quite different. Samples of human pathogen-contaminated produce/plants have been examined mostly by conventional culture methods, polymerase chain reaction (PCR), fluorescence microscopy, or other methods. These studies have provided no definitive information regarding the molecular interactions that may be involved in attachment of human pathogens to plant tissues. However, it is anticipated that future work in this area will provide more fundamental biochemical or genetic data related to attachment. A few examples of studies pertinent to the concepts of plant-human pathogen attachment are presented below and summarized in Table 2.3.
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