Foodborne illness due to Salmonella-contaminated pork products is an important public health problem, causing significant economic losses worldwide. The use of bacteriophages is a potential intervention tool that has attracted interest for the control of foodborne pathogens. The objective of this study was to detect the presence of Salmonella in commercial pig farms and to isolate specific autochthonous bacteriophages against Salmonella Typhimurium, to characterize them and to evaluate their lytic capacity against Salmonella Typhimurium in vivo and in vitro. Salmonella was isolated on 50% (4/8) of the farms, with serotype Typhimurium being the most prevalent, detected in 48.2% of samples (13/27). The isolated Salmonella Typhimurium bacteriophages belong to the Podoviridae family, were active against serotypes Abony, Enteritidis, Typhi, and Typhimurium, but not against serotypes Arizonae, Cholerasuis, Gallinarum, and Pullorum. In in vitro tests, bacteriophage at 10(7) PFU/mL and 10(9) PFU/mL significantly reduced (p<0.05) Salmonella Typhimurium counts in 1.6 and 2.5 log10 colony-forming units (CFU)/mL, respectively, after 24 h. Before the in vivo treatment with bacteriophages, Salmonella was identified in 93.3% (28/30) of the fecal samples from the pigs inoculated with 10(6) CFU/mL, and only in 56.6% (17/30) after the treatment consisting of oral administration of the pool of the bacteriophages after the fasting period, simulating a common preslaughter practice. These results indicate that the pool of bacteriophages administered was capable of reducing the colonization of Salmonella in pigs.

Numerous studies have assessed the efficacy of phage-based methods to inhibit Salmonella contamination in food products. As with most antibacterials, bacteria can develop resistance to phage in vitro. Here, we applied a single broad-spectrum Salmonella phage, vB_SalS_SJ_2 (SJ2; 10 PFU; MOI = 10), to Salmonella-contaminated meat and eggs to quantify the development of resistance in actual food matrices. Treatment with a single phage significantly reduced Salmonella Typhimurium contamination in both ground pork and liquid egg at various time points. Similarly, the same phage significantly reduced Salmonella Enteritidis in both food matrices. Efficacy was temperature dependent as larger reductions were seen at higher temperatures (21°C) versus lower temperatures (4°C) at 24 h. Following phage treatment, over 10,000 Salmonella isolates were examined for resistance to the treatment phage. The percentages of phage-resistant Salmonella (either serovar) recovered from phage-treated versus untreated pork did not differ. Conversely, significantly (p < 0.05) higher percentages of phage-resistant Salmonella Typhimurium (92.50% vs. 0.56% of control) and Salmonella Enteritidis (50.83% vs. 0.56% of control) isolates were observed in phage-treated versus untreated egg samples after incubation at room temperature for 48 h. Taken together, these data indicate that the food matrix may influence the emergence of phage resistance with resistance developing more rapidly in foods with less complex microbial communities. Future studies will focus on the impact the development of resistance in production and processing settings may have on the efficacy of phage treatments for longer term biocontrol of pathogens.

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Here, we present the genome sequence of the Escherichia coli bacteriophage UFV-AREG1. This phage was isolated from cowshed wastewater and showed specificity for enterohemorrhagic E. coli O157:H7 (ATCC 43895), E. coli 0111 (CDC O11ab) and E. coli (ATCC 23229).