Isolation and characterization of a novel bacteriophage as a biological control agent against multidrug resistant Escherichia coli in compost and agricultural irrigation water [version 1; peer review: awaiting peer review]

Background Escherichia coli is a critical priority pathogen due to its significant morbidity, mortality, and growing antimicrobial resistance, underscoring the urgent need for novel control strategies. This bacterium is frequently implicated in outbreaks associated with horticultural products, particularly those cultivated in organic farming systems. The aim of this study was to isolate and evaluate the potential of a bacteriophage as a biocontrol agent against E. coli in compost and agricultural irrigation water. Methods E. coli presence in compost samples (n=17) was determined through microbiological assays, and the bacterial identity was confirmed by PCR amplification of the phoA gene. Antimicrobial resistance profiles of the isolates were assessed using the disk diffusion method. Bacteriophage isolation was conducted from livestock fecal samples using a double-layer agar technique. The stability of the bacteriophage under varying pH levels and temperatures was evaluated, along with its replication dynamics. Additionally, the phage’s efficacy in reducing E. coli populations in compost and irrigation water was assessed. Genomic sequencing and bioinformatic analyses of the bacteriophage were conducted to characterize its genetic profile. Results E. coli strains isolated exhibiting multidrug resistance were isolated from compost samples. The isolated bacteriophage, named Alux-21, exhibited stability at neutral pH and retained viability at both 4°C and 40°C over a six-month period. Importantly, the phage achieved a significant reduction of E. coli counts, exceeding 3.8 logs in compost and 3 logs in irrigation water, demonstrating its superior efficacy compared to previously reported phages in similar substrates. Genomic analysis confirmed the absence of virulence-associated, lysogeny, and antibiotic resistance genes. Conclusion The findings highlight Alux-21 as a sustainable biocontrol agent for E. coli in compost and irrigation water. Field validation will be crucial to establish its scalability and efficacy under real-world agricultural conditions.