Therapeutic potential of novel phages with antibiotic combinations against ESBL-producing and carbapenem-resistant Escherichia Coli

The isolated phages, EC.W1-9 and EC.W15-4, belonged to the Podoviridae and Straboviridae families, and lack integrase or toxin-coding genes, indicating safety for therapeutic use. The combination of these phages significently enhanced their lytic ability, lysing 61.7% of 60 E. coli isolates, compared to 41.6%-55% lysis by individual phages. Furthermore, the phage combination demonstrated 100% susceptibility against different E. coli sequence types, including ST73, ST648, ST2311, ST405, ST7962, ST131, ST13003, and ST167. Additionally, synergy between antibiotics and phage combinations improved susceptibility rates to 73.3% for ESBL producers and 54% for CREC. The combined treatment of isolated phages and antibiotics significantly increased survival rates in BALB/c mice exposed to resistant STs of E.coli, including ST131, ST648, and ST410. Survival rates against ST131 increased by approximately 75% and 50% compared to treatment individual phages. Combined treatment with two phages and antibiotics resulted in 75-100% survival against E. coli ST410 and 100% survival against ST648 CONCLUSIONS: This study highlights the therapeutic importance of phage and phage-antibiotic combinations in combating ESBL-producing E. coli and CREC isolates.