AimsPhotobacterium damselae subsp. damselae is a potent histamine-producing micro-organism. The aim of this study was to isolate and characterize a bacteriophage Phda1 that infected P.damselae subsp. damselae to inhibit its growth and histamine accumulation. Methods and ResultsPhda1 was isolated from a raw oyster, and the host range, morphology and the bacteriophage genome size were analysed. Phda1 formed a clear plaque only against P.damselae subsp. damselae JCM8969 among five Gram-positive and 32 Gram-negative bacterial strains tested. Phda1 belongs to the family Myoviridae, and its genome size was estimated as 352-395kb. According to the one-step growth curve analysis, the latent period, rise period and burst size of Phda1 were 60min, 50min and 19plaque-forming units per infected cell, respectively. Divalent cations, especially Ca2+ and Mg2+, strongly improved Phda1 adsorption to the host cells and its propagation. Phda1 treatment delayed the growth and histamine production of P.damselae subsp. damselae in an invitro challenge test. ConclusionsThe bacteriophage Phda1 might serve as a potential antimicrobial agent to inhibit the histamine poisoning caused by P.damselae subsp. damselae. Significance and Impact of the StudyThis is the first description of a bacteriophage specifically infecting P.damselae subsp. damselae and its potential applications. Bacteriophage therapy could prove useful in the prevention of histamine poisoning.