Bacteriophages RCF and 1-6bf can control the growth of avian pathogenic Escherichia coli

Escherichia coli (E. coli) is a widely distributed pathogenic bacterium that poses a substantial hazard to poultry, leading to the development of a severe systemic disease known as colibacillosis. Colibacillosis is involved in multimillion-dollar losses to the poultry industry each year worldwide. Avian pathogenic E. coli is also involved in causing meningitis and urinary tract infections in humans. This creates a significant risk to public health. The increasing incidence of multidrug-resistant illnesses and the failure of antibiotics in human and veterinary medicine have led to a pressing demand for alternate approaches. This study investigates the possibility of bacteriophages as an acceptable substitute for antibiotics in managing E. coli infections in poultry. In the current study, two novel phages targeting E. coli (EP1) strain were isolated from sewage water and thoroughly characterized in vitro. Transmission electron microscopy reveals that Rcf and 1-6bf belong to the "Podoviridae" and "Caudovirales". Rcf has an icosahedral capsid of 18 nm with a tail size of 5 nm, while 1-6bf has an elongated head capsid of 93 nm and a short non-contractile tail of 8 nm with tail fibers for attachment. RCF and 1-6bf have genome sizes of 38 kb and 77 kb, with GC content of 50.98 % and 42.1 % respectively. Notably, phage 1-6bf displayed remarkable tolerance to high temperatures, retaining lytic activity at 95°C. Both phages effectively controlled host bacterial growth for up to 12 h post-infection. Rcf and 1-6bf produce clear plaques with a latent period of 10 min and 5 min with a burst size of 85 and 220 PFU/cell respectively.