Bacteriophages are bacterial viruses and consist of a single- or double-stranded DNA or RNA protected by a protein capsid. They are able to infect bacteria by injecting their nucleic acids inside the host. The viruses multiply and induce lysis of the host cell, or they are stabilized as prophage, either inserted in the bacterial genome or as independent plasmid molecules. Bacteriophages represent the most numerous micro-organisms found on earth and play a major role in bacterial evolution by serving as a genomic reservoir in the environment and by promoting lateral gene transfer among bacteria through transduction. They also play a role in bacterial virulence through lysogenic conversion by encoding virulence factors. Bacteriophages, as well as their recombinant derivatives, are now used in a multitude of applications in the biotechnology and medical fields (e.g., as an alternative to antibiotics; tools for screening libraries of proteins, peptides or antibodies; vectors for protein and DNA vaccines; or as gene therapydelivery vehicles). Although most bacteriophages do not represent a threat to human health (unless they are carrying virulence factors), the use of recombinant viral particles in some instances might raise some biosafety concerns by bringing and potentially disseminating new genetic traits among bacterial populations. A thorough risk assessment evaluating the properties of the manipulated bacteriophages may be required to implement adequate containment and control measures to protect human health and the environment. This article describes the general characteristics of bacteriophages that could pose a risk to human health and the environment. Several aspects that should be addressed when manipulating them in laboratories are discussed, with illustrations of relevant examples. Finally, based on the risk assessment conclusion, biosafety recommendations (work practices, safety equipment, and waste management) are proposed.
