impact of multiplicity of infection (moi) on in-vitro phage therapy against xanthomonas axonopodis pv. citri

Background: antimicrobial resistance (amr) is an escalating global health concern, with the rapid emergence of multidrug-resistant (mdr) pathogens outstripping the development of new antibiotics. bacteriophages (phages), which specifically target and lyse bacteria, represent a promising alternative. this study investigated the therapeutic potential of phages against xanthomonas axonopodis pv. citri, a significant bacterial pathogen causing citrus canker and considerable economic losses worldwide. methods: phages were isolated from diverse environmental sources (e.g., soil and citrus fruit samples) and screened for lytic activity against x. axonopodis pv. citri. phage purification and titer determination were performed using the double-layer agar method. the ability of phages to suppress bacterial growth was assessed in vitro via optical density (od₆₀₀) and colony-forming unit (cfu) counts over 24 hours across a range of multiplicities of infection (mois). results: the isolated phages exhibited a narrow host range and high stability at 7°c, with an average titer of 201 plaques per plate upon purification. in vitro assays confirmed that the phages successfully suppressed the growth of x. axonopodis pv. citri, demonstrating strong lytic activity and significant reduction in bacterial loads. phages 1p, 2p, 3p, and 5p showed varying degrees of effectiveness, with notable suppression at mois of 0.01, 10, and 100. phage 3p provided sustained bacterial suppression at moi 10, while phage 2p showed consistent activity across all tested mois. despite observations of transient bacterial resistance, all phages maintained their antibacterial efficacy. conclusion: our findings underscore the therapeutic potential of bacteriophages as an effective and sustainable alternative to antibiotics for controlling x. axonopodis pv. citri. the demonstrated lytic activity and bacterial suppression, even at varying mois, suggest that phage therapy offers a viable strategy against antibiotic-resistant strains. furthermore, the cost-effectiveness of phage therapy provides a compelling rationale for its expanded consideration in addressing the global antibiotic resistance crisis within the broader context of healthcare economics.