Purpose: To assess the comparative post-contamination consequences on cilantro, in model systems, with attenuated isolates of S. enterica and E. coli O157:H7 during open-field production, sequential harvest and crop re-growth, and in simulated postharvest washing.
Methods: Two cultivars of cilantro, Santo and Leisure, were grown under open field conditions and spray-inoculated with two inoculum doses (log 4 and log 6 CFU/ml) of attenuated strains of E. coli O157:H7 and S. entericasv. Typhimurium. Cilantro was harvested at commercial maturity stage, processed in a model wash system amended with NaClO (50 mg/l, pH 6.5) and stored for 14 days at 5 °C or 12.5 °C. Quantitative and qualitative survival of the pathogens was monitored after 12 h, 6 and 12 days post inoculation (dpi), following wash processing, and 7 and 14 days post washing. The effect of delays to cooling after harvest and the persistence of the pathogens in sequential cuttings and re-growth intervals was also evaluated.
Results: No significant variability of attached E. coli O157:H7 and Salmonella was observed as a function of cultivar. Salmonella and E. coliO157:H7 populations declined after inoculation below the limit of quantitative detection, but viability was demonstrated after 12 dpi following selective enrichment. Washing with 50 mg/l of NaClO was not sufficient to disinfect the inoculated cilantro (log 6) prior to refrigerated storage. Viable populations of both pathogens were confirmed throughout the storage interval. No applied bacteria were detected 22 days after re-growth of cilantro plants in the field.
Significance: This study provides preliminary risk-based data that will be useful for the development and adoption of preventive controls in food safety management among cilantro growers and processors.