Photobacterium damselae subsp. damselae at the animal-human interface: ecology, pathogenicity, and genomic gaps in a changing climate.

Photobacterium damselae subsp. damselae (Pdd) is a Gram-negative bacillus with zoonotic potential and wide global distribution. Found primarily in marine ecosystems, Pdd has been reported in diverse hosts, including fish, mollusks, crustaceans, marine mammals, sea turtles, birds, and humans. Infection dynamics are influenced by host factors such as environmental stress and pre-existing conditions, while clinical signs are frequently non-specific, making misdiagnosis likely. Its virulence involves iron acquisition systems, a polysaccharide capsule, hemolysins, and other cytotoxic enzymes, some of which are plasmid-encoded and whose expression is influenced by environmental conditions such as water temperature and salinity. This narrative review reports the current knowledge on Pdd's pathogenic mechanisms, ecological traits, diagnostic approaches, and histopathological features of infections reported in various hosts. It also addresses antimicrobial resistance patterns and alternative prevention and control strategies, available genomic data, and future bioinformatics perspectives. As a conceptual framework, we propose climate change as a dual driver that compromises host defenses and may promote pathogen persistence and virulence, thereby potentially facilitating opportunistic infections and cross-species transmission. By highlighting knowledge gaps, this review aims to inform future surveillance efforts and interdisciplinary research on the ecological and epidemiological dynamics of Pdd in wildlife, livestock, domestic animals, and humans.