these pathogens. One of these alternatives is the use of bacteriophages, a very old idea that continues to be used in human health in countries such as Russia, (reported in the CBC program, ‘The Nature of Things’) to deal with bacterial pathogens of the intestine (Stone, 2002). Lytic bacteriophages are viruses that attach to specific receptors on the surface of bacteria, inject their DNA, and express genes that lead to the synthesis of new phages. This process ends with the programmed lysis (death) of the host bacterium, and the release of many more phages. The therapeutic use of phages as antimicrobial agents has a number of advantages compared with other methods. Firstly, phages are highly specific and allow for the removal of the specifically targeted microorganisms from a mixed population. Secondly, unlike antibiotics that decay over time, numbers of phages actually increase and work their way more deeply into pockets of infection. Furthermore, phages are living entities that adapt and evolve; they can pass from host to host, and have the potential to establish an infectious cure. Interest in agricultural applications of phages is now expanding rapidly in three major areas: •
phage control of plant diseases such as bacterial spot on tomatoes and
Erwinia sp. infections of fruit trees (fire blight) and root crops (soft rot). •
phages to treat diseases of animals, eg, respiratory infections caused by
E. coli in chickens, furunculosis (A. salmonicida) in fish, and mastitis in cattle. •
phages to control human food-borne pathogens such as Salmonella spp. in chickens, E. coli (O157:H7) in cattle, and Listeria spp. during the processing of food (Brabban et al, 2003). In reference to humans, it has been reported that some investigators are
attempting to use phages to control MRSA (methicillin-resistant Staphyloccus
aureus), a bacterial organism that is responsible for the vast majority of serious infections that originate in hospitals (von Radowitz, 2003).
70