wksl3, a New Biocontrol Agent for Salmonella enterica Serovars Enteritidis and Typhimurium in Foods: Characterization, Application, Sequence Analysis, and Oral Acute Toxicity Study

Abstract

cOf the Salmonella enterica serovars, S. Enteritidis and S. Typhimurium are responsible for most of the Salmonella outbreaks implicated in the consumption of contaminated foods in the Republic of Korea. Because of the widespread occurrence of antimicrobial-resistant Salmonella in foods and food processing environments, bacteriophages have recently surfaced as an alternative biocontrol tool. In this study, we isolated a virulent bacteriophage (wksl3) that could specifically infect S. Enteritidis, S. Typhimurium, and several additional serovars. Transmission electron microscopy revealed that phage wksl3 belongs to the family Siphoviridae. Complete genome sequence analysis and bioinformatic analysis revealed that the DNA of phage wksl3 is composed of 42,766 bp with 64 open reading frames. Since it does not encode any phage lysogeny factors, toxins, pathogen-related genes, or food-borne allergens, phage wksl3 may be considered a virulent phage with no side effects. Analysis of genetic similarities between phage wksl3 and four of its relatives (SS3e, vB_SenS-Ent1, SE2, and SETP3) allowed wksl3 to be categorized as a SETP3-like phage. A single-dose test of oral toxicity with BALB/c mice resulted in no abnormal clinical observations. Moreover, phage application to chicken skin at 8°C resulted in an about 2.5-log reduction in the number of Salmonella bacteria during the test period. The strong, stable lytic activity, the significant reduction of the number of S. Enteritidis bacteria after application to food, and the lack of clinical symptoms of this phage suggest that wksl3 may be a useful agent for the protection of foods against S. Enteritidis and S. Typhimurium contamination.

A proposed new bacteriophage subfamily: “Jerseyvirinae”

“…In phage P22, the tailspike facilitates adsorption to Salmonella O-antigen 12 of the cell surface LPS, which is expressed by members of White-Kauffmann-Le Minor serogroups A, B and D1 [22]. The high degree of conservation of the P22-like domain and catalytic residues, combined with host-range data for SETP3, SETP7, SETP13, vB_SenS-Ent1 and wksl3 [14,29,56], suggests that "Jerseylikevirus" members isolated to date are limited to these Salmonella serogroups. However, SS3e appears to be an exception: it has been reported to be capable of lysing enterobacteria other than Salmonella, including E. coli, Enterobacter cloacae, Shigella sonnei, and Serratia marcescens [56].…”

Salmonella Phages and Prophages: Genomics, Taxonomy, and Applied Aspects

“…120 nm × 7 nm, and a 20 nm baseplate with spikes. Importantly, a high level of nucleotide identity (up to 93 % of identity between wksl3 and SS3e) is a distinctive feature of this phage genus [ 55 ].…”

Biocontrol of Salmonella Enteritidis in spiked chicken cuts by lytic bacteriophages ΦSP-1 and ΦSP-3

“…The phage treatment on samples inoculated with Salmonella at 5 °C reduced the bacterial counts up to 2.3 log 10 CFU/cm 2 . Similarly workers from Korea demonstrated the ability of phage wksl3 on Salmonella strains (log 10 3.25 CFU cm 2 of skin) inoculated on chicken skin at a lower temperature of 8 °C to completely eliminate the host cells over the 1‐week test period .…”