American-Eurasian Journal of Scientific Research 11 (3): 199-208, 2016 ISSN 1818-6785 © IDOSI Publications, 2016 DOI: 10.5829/idosi.aejsr.2016.11.3.23015 Corresponding Author: Ayalew Negash, University of Gondar, Faculty of Veterinary Medicine, Gondar, Ethiopia, P.O. Box. 196. 199 Review on Bacteriophages and its Antimicrobial Uses Ayalew Negash and Mebrat Ejo University of Gondar, Faculty of Veterinary Medicine, Gondar, Ethiopia Abstract: Bacteriophages, also called phages, are obligate intracellular parasite that infect bacteria and reproduce by taking their host’s biosynthetic pathways. They are the most abundant living entities on earth which affect the abundance and evolution of bacterial species. Two categories of bacteriophages are recognized; temperate and virulent, which propagate in two possible ways; lytic life cycle and lysogenic life cycle. They have been characterized by their host range and the physical characteristics, including capsid size, shape and structure, as well as genome size and type. These advances can have a profound impact on the development of safe therapeutic phage preparations having optimal efficacy against their specific bacterial hosts in humans and animals. Bacteriophages have been reported to be effective in treating various bacterial diseases such as cerebrospinal meningitis, skin infections, hepatic abscesses, lung infections, eye infections and urinary tract infections. Although phage therapy has been historically associated with the use of bacteriophages in human medicine, phages also have been extensively used in veterinary medicine. In conclusion, use of bacteriophages as antimicrobial is an excellent alternative for the treatment of bacterial infections. Therefore, optimization of formulations and long-term stability data is required before it can be widely used within a clinical setting. Key words: Animal Antimicrobial Bacteriophage Human INTRODUCTION Two categories of bacteriophages are recognized; Bacteriophages are viruses that infect bacteria. possible ways; lytic life cycle and lysogenic life cycle [7]. They are the most abundant living entities on earth which During lytic infection, virulent phages inject their nucleic affect the abundance and evolution of bacterial species, acid into the host cell following attachment. Expression of since several bacteriophages exist on the planet [1]. the phage genome directs the cellular machinery of the Bacteriophages were discovered by Fredrick Twort and host to synthesize new phage capsule material. The Felix d’Herelle, whom d'Herelle called bacteriophages resulting phage progeny are released by fatal cell lysis (eaters of bacteria) [2]. enabling the lytic cycle to continue as new cells are Bacteriophages, also called phages, are obligate infected. The number of progeny released (burst size) intracellular parasite that infect bacteria and reproduce by varies from 50-200 new phage particles [1]. In contrast, taking their host’s biosynthetic pathways [3]. It depends during lysogenic infection, temperate phage nucleic on the host for its propagation, which is influenced by a acid recombines with the host cell genome forming a variety of factors such as temperature, nutrients, light dormant prophage. The prophage is reproduced in the and other environmental forces [4]. These bacterial host cell line and confers immunity from infection by the viruses have genetic material in the form of either DNA same type of phage. Stress conditions such as ultraviolet or RNA, encapsidated by a protein coat. Bacterial light or chemical mutagens can induce a switch to the lytic genomes have revealed that phage genome elements are cycle [8]. an important source of sequence diversity and can The number of phages that has been isolated and potentially influence pathogenicity and evolution of characterized likely represents only a tiny fraction of the bacteria [5]. phages existing on earth and phages with new In theory, all bacteria are susceptible to viral characteristics are continuously being isolated from infection, often by several types of phages [6]. different parts of the world [9, 10, 11]. Nowadays when temperate and virulent, which propagate in two