Prevalence of Foodborne Pathogens in Fresh Produce in the U.S.-Data from the USDA Microbiological Data Program (MDP)

Introduction: The Microbiological Data Program (MDP), initiated by USDA-Agricultural Marketing Service (AMS) in 2001, provides data on targeted pathogens in select fruit and vegetables. This data is available to federal, state agencies and the produce industry for food safety decision making purposes, risk modeling, and trend analysis. This program coordinates its activities with CDC, FDA and the National Agricultural Statistics Service (NASS).

Purpose: To provide information on the evolution of the program, present data on sampling, number and type of pathogens isolated, serotypes, PFGE data, and antimicrobial resistance characteristics.

Methods: Different produce commodities were collected every month from 11 participating states to represent about 50 percent of the population and different regions in the country.  Samples were analyzed in eight (8) state laboratories for Salmonella spp., E.coli O157: H7, Non-O157 Shiga toxin E.coli (STEC) and Listeria monocytogenes.

Results:  From 2001-2008, there were 0.05% (38/74,988) positives for Salmonella and 0% (0/42,784) for E.coli O157: H7.  From 2009-2011, the positive rate trended upward following method improvements to 0.15% (80/52,126) for Salmonella and 0.01% (2/14,756) for E.coli O157: H7. During these two periods, the program detected 0.11% (25/21,515) vs. 0.14% (70/49,862) non-O157 STEC. Testing for L. monocytogenes began in October 2011 and has detected 0.4% (4/1,015) positives. Cilantro and spinach samples had the highest number of positives for Salmonella spp. and non-O157 STEC and a wide range of serotypes were detected. The Pulsed Field Gel Electrophoresis (PFGE) patterns of the isolates were uploaded to CDC’s PulseNetfacilitating early identification and investigation of common source outbreaks. The antimicrobial resistance characteristics were reported to CDC’s NARMS database. The FDA used MDP data for investigations, initiating voluntary recalls, and developing guidance letters to growers.

Significance: MDP collects statistically relevant microbiological data on both domestic and imported fresh produce and is the only federal program monitoring for non-O157 STEC in produce.