Eighteen-month Stability of <i>Myoviridae</i> Bacteriophages under Refrigeration Temperatures for Therapeutic Applications

Background: Rising antimicrobial resistance, especially in Pseudomonas aeruginosa, has renewed interest in Myoviridae phages as therapeutic agents. Their long-term stability under refrigeration remains a key challenge. This study was conducted to examine the stability and therapeutic potential of three Myoviridae bacteriophages (PA45, PA32, and PA6) stored at refrigeration temperatures (approximately 4°C with minor variations) over 18 months. Methods:The refrigerator temperature was checked weekly using a manual thermometer. Regular enrichment was performed on a monthly basis to maintain phage infectivity. Phage titers were measured using the double-layer agar method. Results: Results indicated that jumbo phage PA32 retained over 90% of its infectivity, PA45 retained about 85%, and PA6 retained approximately 70% of its initial level. Conclusion: These findings highlight refrigeration as a viable and practical approach for long-term phage storage, particularly in resource-limited settings.