Integrated Morphological, Functional, and Genomic Analysis of a Novel Lytic Phage (VIT_AJPSC) Infecting Multidrug-Resistant Shigella dysenteriae.

Bacteria are historically known to cause a disproportionate number of deaths because of infectious diseases worldwide. Annually, 55 million deaths are accounted for because of bacterial infections, out of which approximately 3 million deaths are because of diarrhoea and dysentery. Shigellosis is an infectious disease caused by Shigella species, and it targets the intestinal tract. It is characterised by acute diarrhoea mixed with blood. The oral antibiotics recommended for shigellosis are ciprofloxacin and azithromycin, with ciprofloxacin as the first-line treatment. Recently, Shigella species have shown a rapid increase in resistance to these antibiotics, which is leading to overdose and prolonged treatment for the same. There is a need of the hour to find a potential substitute for antibiotics. Many alternatives, such as antimicrobial peptides, plant-based substances, bacteriophages, and probiotics, have shown promise compared to antibiotics. This paper focuses on the isolation and characterization of bacteriophages against Shigella dysenteriae. Bacteriophages are viruses that kill bacteria and are very specific to their host. They require host machinery to replicate; therefore, there is very little chance of developing resistance in bacteria against phage. The paper describes screening and isolation of phages from environmental samples against Shigella dysenteriae, followed by optimization studies and their characterization, such as host range, burst size and one-step growth curve. Morphological characterization using transmission electron microscopy (TEM) and whole genome sequencing has been performed, indicating that the phage belongs to the Myoviridae family and has a genome size of 38kbp.