Bacteriophages present huge potential both as a resource for developing novel tools for bacterial diagnostics and for use in phage therapy. This potential is also valid for bacteriophages specific for Yersinia enterocolitica. To increase our knowledge of Y. enterocolitica-specific phages, we characterized two novel yersiniophages. The genomes of the bacteriophages vB_YenM_TG1 (TG1) and vB_YenM_R1-RT (R1-RT), isolated from pig manure in Canada and from sewage in Finland, consist of linear double-stranded DNA of 162,101 and 168,809 bp, respectively. Their genomes comprise 262 putative coding sequences and 4 tRNA genes and share 91% overall nucleotide identity. Based on phylogenetic analyses of their whole-genome sequences and large terminase subunit protein sequences, a genus named Tg1virus within the family Myoviridae is proposed, with TG1 and R1-RT (R1RT in the ICTV database) as member species. These bacteriophages exhibit a host range restricted to Y. enterocolitica and display lytic activity against the epidemiologically significant serotypes O:3, O:5,27, and O:9 at and below 25°C. Adsorption analyses of lipopolysaccharide (LPS) and OmpF mutants demonstrate that these phages use both the LPS inner core heptosyl residues and the outer membrane protein OmpF as phage receptors. Based on RNA sequencing and quantitative proteomics, we also demonstrate that temperature-dependent infection is due to strong repression of OmpF at 37°C. In addition, R1-RT was shown to be able to enter into a pseudolysogenic state. Together, this work provides further insight into phage-host cell interactions by highlighting the importance of understanding underlying factors which may affect the abundance of phage host receptors on the cell surface. IMPORTANCEOnly a small number of bacteriophages infecting Y. enterocolitica, the predominant causative agent of yersiniosis, have been previously described. Here, two newly isolated Y. enterocolitica phages were studied in detail, with the aim of elucidating the host cell receptors required for infection. Our research further expands the repertoire of phages available for consideration as potential antimicrobial agents or as diagnostic tools for this important bacterial pathogen.Y ersinia enterocolitica, a facultative anaerobic, Gram-negative, nonsporulating, short bacillus isolated frequently from soil, water, animals, and foods, is an important zoonotic pathogen leading to human and animal enteric infection (1). The main animal reservoir for Y. enterocolitica is pigs, and pork-derived products are thought to be the main source of human infections, in addition to the drinking of contaminated water and blood transfusions (1, 2). Symptoms of yersiniosis may include diarrhea, terminal ileitis, mesenteric lymphadenitis, and septicemia (3). Among the species within the genus Yersinia, Y. enterocolitica is highly heterogeneous and is grouped into six phylogroups (4). The widely used bioserotype groups form the basis of the phylogroups such that phylogroup 1 contains the biotype 1A strains,...

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Bacillus cereus is a pathogenic adulterant of raw milk and can persist as spores and grow in pasteurized milk. The objective of this study was to determine the prevalence of B. cereus and its enterotoxins in pasteurized milk at its best-before date when stored at 4, 7, and 10°C. More than 5.5% of moderately temperature-abused products (stored at 7°C) were found to contain >10 CFU/mL B. cereus , and about 4% of them contained enterotoxins at a level that may result in foodborne illness; in addition, more than 31% of the products contained >10 CFU/mL B. cereus and associated enterotoxins when stored at 10°C. Results from a growth kinetic study demonstrated that enterotoxin production by B. cereus in pasteurized milk can occur in as short as 7 to 8 days of storage at 7°C. The higher B. cereus counts were associated with products containing higher butterfat content or with those produced using the conventional high-temperature, short-time pasteurization process. Traditional indicators, aerobic colony counts and psychrotrophic counts, were found to have no correlation with level of B. cereus in milk. The characterization of 17 representative B. cereus isolates from pasteurized milk revealed five toxigenic gene patterns, with all the strains carrying genes encoding for diarrheal toxins but not for an emetic toxin, and with one strain containing all four diarrheal enterotoxin genes (nheA, entFM, hblC, and cytK). The results of this study demonstrate the risks associated even with moderately temperature-abused pasteurized milk and the necessity of a controlled cold chain throughout the shelf life of fluid milk to enhance product safety and minimize foodborne illness.

BackgroundBacteriophage vB_YenP_AP5 is a lytic bacteriophage capable of infecting Yersinia enterocolitica strains of serotype O:3, an epidemiologically significant serotype within this bacterial species that causes yersiniosis in humans. This work describes the complete genome sequence of this phage.ResultsThe genome consists of linear double-stranded DNA of 38,646 bp, with direct terminal repeats of 235 bp in length, and a GC content of 50.7%. There are 45 open reading frames which occupy 89.9% of the genome. Most of the proteins encoded by this virus exhibit sequence similarity to Yersinia phage φYeO3-12 and Salmonella phage φSG-JL2 proteins.ConclusionsGenomic and morphological analyses place the bacteriophage vB_YenP_AP5 in the T7likevirus genus of the subfamily Autographivirinae within the family Podoviridae.