Isolation and characterization of a broad-spectrum bacteriophage against multi-drug resistant Escherichia coli from waterfowl field.

Escherichia coli (E. coli) is a significant pathogen responsible for intestinal infections and foodborne diseases. The rise of antibiotic resistance poses a significant challenge to global public health. Traditional antibiotic therapy is becoming increasingly ineffective, highlighting the urgent need for innovative control strategies. This study explores the potential of bacteriophages as a sustainable alternative to traditional antibiotics. From 2021 to 2022, a total of 183 non-repetitive duck source fecal samples were collected from Mianyang City, Sichuan Province, and 126 strains of E. coli were isolated. The minimum inhibitory concentration (MIC) test showed that these strains exhibited high resistance to piperacillin (96.8%), tetracycline (88.9%), and chloramphenicol (86.5%). It is concerning that 93.7% of the isolates are classified as multidrug-resistant (MDR), posing a significant threat to existing treatment options. 20 bacteriophages were isolated from fecal and soil samples, among which 5 bacteriophages were selected for further analysis. Bacteriophage YP6 showed excellent lytic effects on MDR strains, especially strain MY104, as well as representative serotypes O1 (E. coli MY51) and O18 (E. coli MY106). The identification of YP6 as a member of the Myoviridae family was conducted using transmission electron microscopy, and it was found to have an optimal infection factor of 0.1. Bacteriophages exhibit significant thermal and pH stability, maintaining survival at temperatures up to 60 °C and pH ranges of 4 to 10. Whole genome sequencing confirmed that YP6 has a double stranded DNA genome of 139,323 base pairs (bp), and no antibiotic resistance or virulence genes were found, indicating a low possibility of horizontal gene transfer. In addition, YP6 effectively inhibits the formation of E. coli biofilm, which is a key factor in chronic infections. The in vivo experiments using Galleria mellonella (G. mellonella) larvae have shown that it has a significant protective effect against MDR E. coli infection. In summary, bacteriophage YP6 is expected to become a therapeutic agent against MDR E. coli infection due to its broad host range, environmental stability, and biofilm inhibition properties. Future research should optimize bacteriophage preparations, evaluate the safety and efficacy of animal models, and establish clinical application plans in the field of food safety.