A Novel and Effective Therapeutic Method for Treating Aeromonas schubertii Infection in Channa maculata

Simple Summary Aeromonas schubertii is one of the most significant opportunistic pathogen threats to humans, other mammals, and aquatic animals. Lytic bacteriophages have been recognized as effective alternatives to antibiotics for controlling bacterial infections. In this study, a lytic bacteriophage, which could effectively infect A. schubertii, was isolated for the first time. We report some of the characteristics of the phage, including its morphology, host range, storage stability, and structural proteins. Furthermore, in vivo experimental infections included intraperitoneal injection and immersion administration to evaluate the effects of phage therapy for A. schubertii infection. Our results suggest a potential use for phage SD04 in controlling this disease. Current experimental data indicate the value of using phage SD04 to prevent A. schubertii infection in snakehead. Aeromonas schubertii is a pathogen that severely affects aquatic animals, including the snakehead, Channa maculata. Lytic bacteriophages have been recognized as effective alternatives to antibiotics for controlling bacterial infections. However, there have been no reports of A. schubertii phages as far as we know. In this study, a lytic bacteriophage SD04, which could effectively infect A. schubertii, was isolated from pond water cultured with diseased snakehead. The SD04 phage formed small, round plaques on Petri dishes. Electron microscopy revealed a hexagonal head and a contractile tail. Based on its morphology, it may belong to the Myoviridae family. Two major protein bands with molecular weights of 50 and 38 kilodaltons were observed after the phage was subjected to SDS-PAGE. The phage showed a large average burst size, high specificity, and a broad host range. When stored at 4 degrees C, phage SD04 had high stability over 12 months and showed almost no variation within the first six months. All fish were healthy after both intraperitoneal injection and immersion administration of SD04, indicating the safety of the phage. After treatment with SD04, Channa maculata in both phage therapy groups and prevention groups showed high survival rates (i.e., 83.3 +/- 3.3% and 100 +/- 1.3%, respectively). Phage therapy inhibits bacterial growth in the liver, the target organ of the infected Channa maculat. The experimental results indicate the potential use of phage SD04 for preventing A. schubertii infection in Channa maculata.