Summary of the USDA MDP Analysis for Salmonella spp. and E. coli with Associated Virulence Factors for Cantaloupe, Celery, Leaf Lettuce, Romaine Lettuce, and Tomatoes
No. of samples tested for Salmonella
No. of samples samples testing testing positive for tested for positive for E. coli with a
E. coli Salmonella spp. virulence factor
Produce item spp.
0 (0.0%) 0 (0.0%) 3 (0.14%) 0 (0.0%) 0 (0.0%) 3 (0.03%)
Leaf lettuce Romaine lettuce
Adapted from USDA, Microbiological Data Program Progress Update and 2002 Data Summary, www.ams.usda.gov/science/mpo/MDPSumm02.pdf, 2004.
and analyzed for E. coli, 64 samples (0.62% of the total number of samples) were found to have detectable levels of E. coli with associated virulence factors. Twenty-seven (1.25%) of 2161 leaf lettuce and 29 (1.34%) of 2158 romaine lettuce samples were found to have detectable levels of E. coli with associated virulence factors. Cantaloupe, celery, and tomato had incidence rates for the presence of E. coli with associated virulence factors of 0.19, 0.14, and 0.11%, respectively.
Follow-up FDA farm investigations and other information from both the agency's imported and domestic produce surveys indicated that failure to follow GAPs was often associated with the findings of pathogen contamination. In particular, inadequate manure management and lack of appropriate field and transport sanitation practices were most frequently associated with overall contamination. Specific problems included fields that were open to domestic animals or were fertilized by untreated animal manure, equipment and tools that were not being sanitized, unsanitary harvesting and/or packing equipment or practices (e.g., woven plastic bags to collect cilantro after harvest), and unsanitary methods of transportation (e.g., trucks washed with nonchlorinated water and/or cleaned infrequently) .
1.4.4 Produce-Associated Foodborne Illness Traceback Investigation Results
Traceback investigations have yielded no definitive information as to the causes of recent produce-associated foodborne illness outbreaks. The inability to identify clearly where contamination occurred and the actual causes of recent foodborne illness outbreaks associated with produce consumption is frustrating to the industry and regulators alike and is a significant hurdle to developing a means of ensuring that similar outbreaks do not recur. Without science-based data that clearly identify the cause of recent foodborne illnesses associated with produce consumption, only speculation and opinion can be used to hypothesize about what may have gone wrong. It is imperative that industry, academia, government, and consumers collaborate and take an active role by working together on developing and implementing measures that enhance produce food safety. Guzewich  reported in a summary of produce-related outbreak farm investigations that the practices most likely to have contributed to numerous recent outbreaks related to produce consumption are:
• Questionable practices regarding safe water use.
• Inadequate animal management (domestic and/or wild animals).
• Unsanitary facilities and equipment.
• Inadequate employee health and hygiene practices.
It is important that future investigations do not simply focus on the suspected primary causes of produce contamination in the supply chain, but allow for identification of hitherto unidentified actual causes of produce contamination. Regulatory agency traceback investigations of facilities suspected of being involved in a foodborne illness outbreak must focus on determining the efficiency and effectiveness of the facilities' GAP program and attempt to identify clearly if the contamination occurred due to non-compliance with GAPs or due to deficiencies in GAPs as they are currently formulated.
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