Isolation and therapeutic potential of phage vB_EcoM_GXW16 against a drug-resistant avian pathogenic Escherichia coli strain

Avian pathogenic Escherichia coli (APEC) is a major pathogenic subset of E. coli responsible for avian colibacillosis, representing one of the most common and economically damaging bacterial threats to the poultry industry globally. Currently, clinical treatment mainly relies on antibiotics. However, the widespread prevalence of drug-resistant strains poses a major challenge to global public health. Bacteriophages (phages) have regained significant attention as promising alternatives to antibiotics. In this study, a lytic bacteriophage vB_EcoM_GXW16 was isolated and purified from wastewater samples collected at a poultry farm. The phage exhibited broad lytic activity against a panel of avian-source Escherichia coli isolates (70.91%, 39/55). Its optimal multiplicity of infection (MOI) was 0.001, and it had a latent period of 10 min. The phage also demonstrated tolerance to a range of pH and temperature conditions, surviving at temperatures up to 60°C and within a pH range of 3 to 12. In vitro tests showed that the phage significantly inhibited the growth of drug-resistant E. coli at three different MOIs. Based on morphological observation and phylogenetic analysis, the phage was classified into the genus Dhakaviru, family Myoviridae, class Caudoviricetes. It possesses an icosahedral capsid and a contractile tail. Whole-genome sequencing confirmed that vB_EcoM_GXW16's genome consists of a 170,605 bp double-stranded DNA. Genomic analysis confirmed the absence of genes associated with virulence, antibiotic resistance, or lysogeny, indicating the potential safety of phage vB_EcoM_GXW16 for clinical applications. Subsequently, the therapeutic efficacy of the phage was investigated in a chick Escherichia coli infection model. Results indicate that phage vB_EcoM_GXW16 exhibits potent therapeutic efficacy against the confirmed APEC strain (Escherichia coli O117:H25_E5), successfully protects chickens against APEC infection, improving survival rates, reducing bacterial loads, and alleviating organ damage. In summary, phage vB_EcoM_GXW16 holds promise as a prospective therapeutic candidate due to its broad host range, environmental stability, and favorable in vitro bacteriostatic effects alongside in vivo therapeutic efficacy. It offers a viable alternative to conventional antibiotics for combating drug-resistant Escherichia coli.