Purpose: To identify and characterize Salmonella spp. within tomato production systems on three agriculturally diverse farms.
Methods: Environmental samples were collected during the NC tomato production season in 2012 (July – September) and 2013 (June- September) from 3 farm locations. Field (tomato fruit, blossom, leaf, weeds, soil) and water samples (n = 1010) were analyzed for Salmonella by enrichment using a modified BAM method as well as by real-time PCR. Isolates were serotyped and genotyped by pulse-field gel electrophoresis. Additionally, water samples were enumerated for generic E. coliusing the IDEXX Colilert and quanti-tray 2000 system.
Results: For 2012-2013, Salmonella was isolated in June (10 isolates, 2013 only), July (28 isolates), August (35 isolates) and September (42 isolates); 59% (68/115) of isolates from water, 33% (38/115) from sediment, 4% (5/115) from tomato fruit, and 3% (4/115) from soil. Of the serotypes identified, 28% (32/115) were Paratyphi B (monophasic from water); 12% (14/115) were Newport (water and sediment); 7% (8/115) were Hartford (water and sediment); 4% (three sets of 5/15) were Agona, Montevideo, and Typhimurium (sediment, tomato, and water, respectively); with 1% (1/115) from Berta (sediment). These findings suggest that particular serotypes may dominate unique tomato environmental niches. Generic E. coli, using 235 CFU/100 ml from the proposed FSMA rules, predicted the presence or absence of Salmonellain water samples 81% (39/48) of the time.
Significance: This project provides baseline information on occurrence and environmental reservoirs of Salmonella spp. in tomatoes on diverse NC farms. This information will support science-based recommendations for tomato production practices leading to reduced microbial contamination and protection of public health.