Characterization of a Newly Isolated Phage against Uropathogenic Escherichia coli and Cloning and Purification of Recombinant Endolysin

Abstract

Among most prevalent microbial diseases, urinary tract infections (UTIs) affect about 150 million people every year worldwide. Uropathogenic Escherichia coli strains (UPECs) are the main cause of both complicated and uncomplicated UTIs. Alongside, uropathogens are becoming progressively more resistant to commonly prescribed antibiotics. As a result, alternative strategies for the prevention and treatment of UTIs must be developed, and use of bacteriophages and their products including endolysins are potential options to eliminate UPEC from the urinary tract. The present study aimed at investigating the therapeutic efficiency of a phage (UE-S1) and its endolysin against UPEC. The phage UE-S1 isolated from the sewage water was characterized and it showed strong lytic potential against UPEC (UE1). The phage showed stability over a wide range of temperature (4°C to 55°C) and pH (3 to 11). UE-S1 phage exhibited high adsorption rate and also reduced bacterial growth significantly without the emergence of phage resistance. Additionally, the phage’s host range included different pathogenic strains of Bacillus, Streptococcus, Acinetobacter and E. coli. These parameters suggest the suitability of phage UE-S1 for therapeutic use, but genomic and structural aspects of the phage must be investigated before its applications. Hence, the genome of phage UE-S1 was found 358,076 bp in length, with 595 putative open reading frames (ORFs) and a GC content of 33.72%. The genome of UE-S1 exhibited no antibiotic resistance and virulence genes, and genes encoding for lysogenic cycle were also absent. Absence of integrase and other lysogenic genes confirms the lytic nature of the phage which is essential criteria for therapeutic use of phages. Similarly, lack of virulence and antibiotic resistance genes suggests that phage will not be harmful to the human body. Moreover, different phage products such as endolysins have shown good therapeutic potential. In this case, gene annotation indicated that the protein encoded by orf534 of UE-S1 was an endolysin which belongs to lysozyme family and it may show lytic potential against UPEC. Overall, the results indicated that phage UE-S1 might be a promising therapeutic agent for controlling MDR UPEC in urinary tract infections.