Background In recent years, frequent disease outbreaks during the shellfish nursery phase in China have caused substantial economic losses. Vibriosis is one of the primary pathogenic diseases involved, with Vibrio corallilyticus identified as a major pathogen in shellfish hatcheries in northern China, capable of causing acute mortality in bivalve larvae.

Objective This study systematically investigates the physiological and biochemical characteristics of pathogenic strains, the proteomic profile and enzymatic activities of their extracellular products (ECPs), aiming to identify key virulence factors that influence the pathogenicity of V. corallilyticus toward shellfish larvae. The findings are expected to provide a scientific basis for establishing an integrated prevention and control system for vibriosis during the shellfish nursery period in China.

Methods Three highly pathogenic strains of V. corallilyticus (RSH02, RSH05, RSH08) isolated from shellfish hatcheries in Shandong and Jiangsu provinces were used in the study. The strains were cultured to the logarithmic growth phase, and growth curves were determined. ECPs from the three highly pathogenic strains and one low-pathogenicity strain were prepared simultaneously using the cellophane plate method. The molecular profiles of ECPs from different strains were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) based on molecular sieving effects. Characteristic protein bands of the highly pathogenic strains were selected, and their extracellular protein compositions were identified using mass spectrometry. Finally, protease activity, hemolysin activity, and siderophore production were assessed using specific agar media (protease assay medium, hemolysin identification medium, and chrome azurol s medium).

Results All three highly pathogenic strains exhibited similar growth curves, with a logarithmic growth phase between 8 and 24 hours, and demonstrated strong proteolytic, hemolytic, and siderophore activities. The ECPs of RSH02, RSH05, and RSH08 were enriched with highly active aminopeptidase, peptidase M4, and neutral metalloproteinase, respectively.

Conclusion Although the three highly pathogenic V. corallilyticus strains shared similar growth characteristics, their ECP compositions differed significantly, suggesting that different strains may exert high pathogenicity and tissue-lytic capability through the secretion of specific virulence factors, such as aminopeptidase, peptidase M4, and metalloproteinase. This finding provides new insights into the pathogenic mechanisms of V. corallilyticus.