Prevalence of Salmonella in cucumbers, antibiotic and acid resistances and description of the kinetic behavior with dynamic model during storage

Abstract

This study isolated Salmonella from cucumbers, analyzed the antibiotic resistance and acid resistance for the isolates and developed a dynamic model. Salmonella prevalence in cucumbers and their resistances were determined. To describe the kinetic behavior of Salmonella isolates, the isolates were inoculated into cucumbers, and Salmonella cell counts were enumerated during storage at 10–30°C. The Baranyi model was fitted to the cell count data to calculate kinetic parameters (lag phase duration [LPD] and maximum specific growth rate (μmax)], and a polynomial model was fitted to the kinetic parameters as a function of temperature. The model performance was evaluated with root mean square error (RMSE). Using these models, a dynamic model was developed. Salmonella were detected in 3 of 24 cucumbers, all of which were multidrug‐resistant and one was acid‐resistant. As storage temperature increased, LPD decreased and μmax increased. These models were appropriate with 0.367 of RMSE. These results suggest that cross‐contaminated Salmonella could increase during transportation, and it may lead to human infection.

Development and validation of a neural network model for growth of Salmonella Newport from chicken on cucumber for use in risk assessment

“…In comparison, in this study, growth of Salmonella Newport on cucumber at 8 hr of storage was predicted to be 0.6 log at 20℃, 1.6 log at 25℃, and 3.3 log at 30℃. However, these comparisons are confounded by differences in data collection (Salmonella type, inoculum size, previous history, enumeration method) and modeling methods (regression vs. neural network) and thus, no firm conclusions can be made about why growth was predicted to be higher in this study than in the study of Ha et al (2020).…”

“…In another study, Ha et al (2020) isolated three strains of Salmonella from cucumber and then inoculated them as a mixture (3.6 to 5.2 log) onto cucumber slices (25 g) by dipping. The inoculated cucumber slices were stored in pairs at 10℃ (0 to 96 hr), 20℃ (0 to 48 hr), 25℃ (0 to 48 hr), and 30℃ (0 to 48 hr) and then Salmonella growth over time of storage was determined by viable counts (CFU).…”

“…Growth of Salmonella on the cucumber slices was observed to increase as a function of time and temperature and at 8 hr of storage was predicted to be 0.4 log at 20℃, 1.5 log at 25℃, and 2.1 log at 30℃ (Ha et al, 2020). In comparison, in this study, growth of Salmonella Newport on cucumber at 8 hr of storage was predicted to be 0.6 log at 20℃, 1.6 log at 25℃, and 3.3 log at 30℃.…”

“…For data used in model development, Ha et al (2020) reported coefficients of determination (R 2 ) of 0.996 for the secondary model for lag time and 0.971 for the secondary model for growth rate. F I G U R E 3 Representative residual (observed -predicted) plots for growth of a chicken isolate of Salmonella Newport on cucumber as a function of time and temperature for data used in model development (20, 28, 36℃) or validation (22, 30, 34℃).…”

“…Salad is an RTE food that is often served with chicken and it often contains diced or sliced cucumber. Although growth of Salmonella on cucumber has been investigated (Elexson et al, 2011;Ha et al, 2020), insufficient data were collected for full development and validation of predictive models. In addition, there are no data or models for growth of chicken isolates of Salmonella on cucumber.…”