Efficacy of benzyl isothiocyanate for controlling Salmonella on alfalfa seeds and sprouts

How colonizing alfalfa sprouts modulates the virulence of Shiga toxin-producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC), a significant cause of foodborne illnesses, is often associated with the consumption of fresh produce, including alfalfa sprouts. This study was executed to determine how quickly STEC grows, adapts, and colonizes alfalfa sprouts during production and storage, and whether the pathogen's virulence and infectious doses are affected by physiological adaptation to sprouts as an environment. A reporter STEC O157:H7 EDL933 strain was developed to track the transcription of eae, a virulence gene involved in colonizing human intestinal enterocytes. When the seeds were inoculated with 2.1 × 103 CFU/g of the reporter strain, the pathogen's population increased to 1.5 × 106 CFU/g sprouts within 1.38 days and then remained stable during the remainder of the 5-day sprouting, indicating physiological adaptation to this environment. Seeds were inoculated with ∼108 CFU/g and subsequently treated with 2000 ppm calcium hypochlorite solution, followed by a water-rinse (treated seeds), or just rinsed with water (untreated seeds). After 5 days of sprouting, the resulting fresh sprouts were refrigerated for three days at 4 °C. Sprout samples were collected and treated with 2000 ppm calcium hypochlorite solution and rinsed thoroughly with water before counting internalized STEC, or just water-washed before measuring total STEC. The transcription of eae (normalized to cell count) was the highest on the second day of sprouting, but the transcription of other virulence and stress-related genes varied, with sodA being upregulated in STEC cells. Lethal dose 50 (LD50) to Galleria mellonella, a STEC infection animal model, was lower (i.e., virulence was higher) in total STEC collected from fresh sprouts produced from treated seeds, compared to that from untreated seeds (1.9 × 100 and 6.0 × 101 CFU/larva, respectively). Compared to refrigerated sprouts, the LD50 of STEC from freshly produced sprouts was lower. Based on these findings, it can be concluded that (a) STEC quickly adapts physiologically to sprouts as an environment, (b) transcription of STEC virulence genes changed during sprouts production but generally decreased during refrigeration, and (c) STEC from fresh sprouts grown from sanitizer-treated seeds were more virulent in the animal model, but STEC from refrigerated sprouts were less virulent.

Occurrence and distribution of Salmonella serovars in carcasses and foods in southern Italy: Eleven-year monitoring (2011-2021)

Salmonella is one of the most common agents of foodborne illness. The genus Salmonella includes two species (Salmonella bongori and S. enterica) and six subspecies (enterica I, salamae II, arizonae IIIa, diarizonae IIIb, houtenae IV, and indica VI), each of which contains multiple serotypes associated with animal and human infections. The aim of the study was to evaluate the presence of Salmonella spp. in carcasses of food-producing animals and foods in southern Italy and the serovar distribution among different sources. From 2011 to 2021, a total of 12,246 foods and 982 samples from animal carcasses were collected and analyzed. The overall percentage of positive samples was 5.84% (N = 773) and a significant increase in prevalence was observed by comparing the years 2011-2015 (257, 3.27%) and 2016-2021 (516, 9.61%; p < 0.05). The highest percentage of positive food samples was observed in "Meat and Meat Products" (N = 327/2,438, 13.41%) followed by "Fish and fishery products" (N = 115/1,915, 6.01%). In carcasses, the highest percentage of positive samples was reported from broilers (N = 42/81, 51.85%) followed by buffalo (N = 50/101, 49.50%) and pork (N = 140/380, 36.84%). After typing, the isolates were assigned to the species S. enterica and to the subspecies: enterica (N = 760, 98.32%), diarizonae (N = 8, 1.03%), salamae (N = 3, 0.39%) and houtenae (N = 2, 0.26%). S. Infantis was the most frequently detected (N = 177, 24.76%), followed by S. Derby (N = 77, 10.77%), monophasic S. Typhimurium (N = 63, 8.81%), S. Typhimurium (N = 54, 7.55%), and S. Rissen (N = 47, 6.57%). By comparing the sampling period 2011-2015 with that of 2016-2021, an increase in the prevalence of S. Infantis and monophasic S. Typhimurium and a decrease of S. Typhimurium were recorded (p < 0.05). Thus, present data suggest that, despite the implementation of national and European control strategies to protect against Salmonella, the prevalence of this pathogen in southern Italy is still increasing and a change of national control programs to protect against Salmonella are necessary.