Waxing and cultivar affect Salmonella enterica persistence on cucumber (Cucumis sativus L.) fruit

Abstract

A dearth of knowledge exists on the pathogen-commodity association of Salmonella enterica on cucumber, despite cucumbers being implicated in multiple salmonellosis outbreaks in recent years in the U.S. Data are lacking on cultivar susceptibility to Salmonella colonization in relation to heterogeneity in fruit surface morphology. Further, fruit waxing is a common practice in wholesale cucumber to preserve the water content of fruit and prolong shelf-life, but its impact on epiphytic microbiota is not well studied. This study investigated the survival of Salmonella Newport and S. Javiana on the surface of six cucumber cultivars of varying surface morphology and the effect of fruit waxing on the persistence of S. Newport. S. Newport and S. Javiana were spot inoculated onto fruit of cultivars ‘Marketmore 97’, ‘Patio Snacker’ and ‘Corinto’ (varieties with trichomes or spines), and ‘Bella’, ‘Pepinex’ and ‘Summer Dance’ (glabrous or smooth varieties). Cucumbers were held at room temperature for 24 h before inoculated sections of exocarp were excised for enteropathogen enumeration. S. Javiana persisted at higher populations than S. Newport (1.0 and 1.5 log CFU g−1 exocarp decline, respectively) after 24 h (P < 0.05). Fruit waxing lessened S. Newport population decline after 24 h on all cultivars tested (P < 0.01). While there was a ~2 log CFU g−1 exocarp decline in populations on unwaxed cucumbers, the reduction on waxed cucumbers was ~1 log CFU g−1 exocarp. A cultivar effect was also observed; ‘Summer Dance’ supported consistently higher and ‘Corinto’ and ‘Marketmore 97’ (though for S. Javiana only) consistently lower Salmonella levels. Cultivars with trichomes were associated with lower populations than glabrous cultivars (P < 0.05). Our data showed that Salmonella persistence on fruit differed for the two serotypes tested and that cultivar differences play a role in determining cucumber surface favourability for pathogen colonization. Additionally, fruit waxing may elevate the risk of Salmonella persistence on cucumber.