Purpose: To provide a seasonal characterization of the microbiological safety of the cantaloupe supply from a major domestic production region.
Methods: A multi‐grower/handler study was conducted over three seasons with samples taken after all pre‐shipment handling, whether field or facility‐packed. Honeydew and watermelon (n = 36 - 60) and cantaloupe (n = 200) per packed lot were tested, between 2011 and 2014, for contamination. Full rind composites (1 composite = 3 fruit) were enriched in Universal Pre-enrichment Broth with 0.05% Tween for 18 h at 35°C. For Salmonella, aliquots were then selectively enriched in tetrathionate broth at 42°C for 6 h followed by M Broth for 18 h at 37°C. For Listeria, samples were enriched in Listeria Enrichment Broth with supplements at 35°C for 48 h. For each lot, controls were inoculated with ~ log 1 and ~ log 2 CFU/composite (n = 5 or 10 composites). Aliquots of enriched samples were frozen in glycerol and retained for confirmation if positive by Roka Atlas system. Confirmation for Salmonella or Listeria on XLT4 or CHROMListeria, and by PCR.
Results: Overall, 4870 fruit were tested of which 4,312 were cantaloupe. Seven verified Salmonella were detected (sv. Poona, Newport, Heildelberg – two each, and one Agona), all from cantaloupe. Nineteen Listeria spp. were detected; no L. monocytogenes were detected. When applied individually all control enrichments were positive. When Salmonella and Listeria were combined, 95% and 100% detection was observed for Listeria and Salmonella, respectively, at log 2 and 83% and 100% at log 1.
Significance: The overwhelming outcome of this survey was for a general absence of detection of Listeria spp., no detection of Listeria monocytogenes, and highly isolated detection of Salmonella.