Interactions Between Salmonella enterica Newport, Fusarium spp., and Melon Cultivars

Melons are perishable fruit of high food safety risk, grown in contact with soil and soil-borne organisms. To assess whether food safety risk could be augmented by the presence of soil-borne fungi, this study investigated the relationship between Fusarium spp. that were isolated from the surface of melon and the foodborne pathogen Salmonella enterica. In four repeated trials, rind discs from cultivars, Arava, Athena, Dulce Nectar, Jaune de Canaries, and Sivan fruit, grown in the field and in high tunnels in Maryland were inoculated separately with Fusarium isolates, F. oxysporum, F. fujikuroi, F. armeniacum, and F. proliferatum, with no Fusarium inoculation serving as a control and incubated at 25°C. Salmonella Newport was inoculated onto melon discs 4 d post-Fusarium inoculation and recovered 24 h later. Melon cultivar impacted the retrieval of Salmonella Newport. In all four replicated experiments, one or more of the netted varieties, Arava, Athena, and Sivan, yielded higher Salmonella Newport counts than one or both smooth-rind melons, Jaune de Canaries and Dulce Nectar (p < 0.05). Fusarium inoculation did not have a marked impact on Salmonella retrieval. The average Salmonella count recovered was 5.0 log colony-forming unit (CFU)/mL for both Fusarium-inoculated and uninoculated melons. However, in one trial, Salmonella Newport counts recovered from F. fujikuroi-inoculated melons were higher than all other treatments (8.6 log CFU/mL; p < 0.001), due to high levels of Salmonella recovered from Jaune de Canaries compared with other experiments. The food safety risk of melon did not appear to be enhanced by postharvest colonization with saprophytic Fusarium spp. However, melons with netted rinds appeared to favor Salmonella colonization compared with smooth melons. Choice of melon cultivar may be an important consideration in reducing Salmonella colonization risk in areas where Salmonella may be endemic in the environment.