In recent years it has become widely recognized that bacteriophages have several potential applications in the food industry. They have been proposed as alternatives to antibiotics in animal health, as biopreservatives in food and as tools for detecting pathogenic bacteria throughout the food chain. Bacteriophages are viruses that only infect and lyse bacterial cells. Consequently, they display two unique features relevant in and suitable for food safety. Namely, their safe use as they are harmless to mammalian cells and their high host specificity that allows proper starter performance in fermented products and keeps the natural microbiota undisturbed. However, the recent approval of bacteriophages as food additives has opened the discussion about ‘edible viruses’. In this review, we examine the promising uses of phages for the control of foodborne pathogens and the drawbacks on which more research is needed to further exploit these biological entities.

The endolysin gene (lysH5) from the genome of the Staphylococcus aureus bacteriophage ΦH5 was cloned in Escherichia coli and characterized. The lysH5 gene encoded a protein (LysH5) whose calculated molecular mass and pI were 53.7 kDa and 8.7, respectively.Comparative analysis revealed that LysH5 significantly resembled other murein hydrolases encoded by staphylococcal phages. The modular organization of LysH5 comprised three putative domains, namely, CHAP (cysteine, histidine-dependent amidohydrolase/peptidase), amidase (l-muramoyl-l-alanine amidase), and SH3b (cell wall recognition). In turbidity reduction assays, the purified protein lysed bovine and human S. aureus, and human Staphylococcus epidermidis strains. Other bacteria belonging to different genera were not affected. The lytic activity was optimal at pH 7.0, 37˚C, and sensitive to high temperatures. The purified protein was able to kill rapidly S. aureus growing in pasteurized milk and the pathogen was not detected after 4 h of incubation at 37˚C. As far as we know, this is the first report to assess the antimicrobial activity of a phage endolysin which might be useful for novel biocontrol strategies in dairying.

The genomes of the two lytic mutant Staphylococcus aureus bacteriophages, vB_SauS-phiIPLA35 (phiIPLA35) and vB_SauS-phiIPLA88 (phiIPLA88), isolated from milk have been analyzed. Their genomes are 45,344 bp and 42,526 bp long, respectively, and contain 62 and 61 open reading frames (ORFS). Enzymatic analyses and sequencing revealed that the phiIPLA35 DNA molecule has 3-protruding cohesive ends (cos) 10 bp long, whereas phiIPLA88 DNA is 4.5% terminally redundant and most likely is packaged by a headful mechanism. N-terminal amino acid sequencing, mass spectrometry, bioinformatic analyses, and functional analyses enabled the assignment of putative functions to 58 gene products, including DNA packaging proteins, morphogenetic proteins, lysis components, and proteins necessary for DNA recombination, modification, and replication. Point mutations in their lysogeny control-associated genes explain their strictly lytic behavior. Muralytic activity associated with other structural components has been detected in virions of both phages. Comparative analysis of phiIPLA35 and phiIPLA88 genome structures shows that they resemble those of 12 and 11, respectively, both representatives of large genomic groupings within the S. aureus-infecting phages.

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