Selected Farm Practices For Control Of Both Softrot And Human Pathogens

To minimize the dissemination and proliferation of the harmful microorganisms on growing plants, it is necessary to take preventive measures to intervene in the introduction of contamination sources in the field. Sources of soft-rotting erwinia and pseudomonas [22,28,38] and foodborne human pathogens that may contaminate or infect growing plants in the field have been previously reviewed [99,108]. Preventive measures and good agricultural practices (GAPs) for reducing the contamination of field crops with foodborne pathogens have been suggested in several guidance references including one published by the U.S. Food and Drug Administration [109] and another one by the IFPA [110]. Preventive control strategies for bacterial soft rot have also been reviewed by Eckert and Ogawa [111] and by Lund [6]. A few practices useful for control of both soft-rot bacteria and foodborne human pathogens in the fields are indicated as follows:

• Use seeds and propagation materials that are free of soft-rot bacteria and human pathogens for planting. Although soft-rot erwinia are generally not considered seedborne [22], long-term survival of salmonella and soft-rot pseudomonas in water [112] and on alfalfa seeds destined for sprouting has been reported [113].

• Properly dispose of the decayed plant materials in the field, which can become the inoculum source of soft-rot bacteria [26] and serve as a fertile ground for the proliferation of foodborne human pathogens such as salmonella [14,15].

• Avoid the use of improperly treated manure or compost in the field. Long-term survival of salmonella and E. coli O157:H7 in feces and in partially composted manure or biosolids has been documented [99].

Application of improperly treated compost possibly containing decayed materials may also serve as the inoculum source of soft-rot bacteria.

• Monitor and ensure that water to be used for irrigation, washing, and preparation of protective chemicals is devoid of harmful microorganisms. Both soft-rot bacteria and human pathogens have been known to survive in water for several years [112].

• Harvest the crop at the optimal stage of maturity and with the minimal mechanical injury. It has been reported that the mature crop exhibits a higher level of resistance to attack by soft-rot bacteria [22] and to the colonization by human pathogens [99]. Injured plant surfaces can serve as the points of entry for soft-rot bacteria and as the sites for attachment by human pathogens [56,57].

• Maintain sanitary conditions and enforce good worker hygiene in the field to prevent the contamination of growing or harvested crops with pathogens carried by farm workers. Outbreaks of foodborne illness due to the contamination of fresh produce with foodborne pathogens originating from farm workers have been previously reported [108].

• Use clean and sanitary vehicles for transporting produce from farms to processing plants.

• Keep the orchards and vegetable farms away from domestic and wild animals and far away from poultry and dairy farms. Feces and animal wastes are believed to be the two most important carriers or reservoirs of foodborne human pathogens [109].

• Remove weeds grown in the field, which may become alternative inoculum sources for soft-rot erwinia [42] and human pathogens [100].

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