Overview
Vibrio mediterranei is a Gram-negative marine bacterium that has emerged as a significant pathogen affecting corals, bivalves, and other marine organisms in Mediterranean and global waters. Originally described from seawater, this versatile pathogen gained prominence when its synonym V. shiloi was identified as the causative agent of coral bleaching in Oculina patagonica. Today, V. mediterranei is recognized as an opportunistic pathogen with a broad host range, causing diseases ranging from coral bleaching to mass mortalities in commercially important bivalves.
Affected species (hosts)
Primary Marine Hosts:
- Corals (Oculina patagonica, Cladocora caespitosa) – causes bleaching and tissue damage
- Pen shells (Pinna nobilis) – major mortality events in captive populations
- Bivalves – razor clams (Sinonovacula constricta), oysters (Crossostrea sikamea), mussels (Mytilus galloprovincialis)
- Manila clams (Venerupis philippinarum) – aquaculture pathogen
Secondary Marine Hosts:
- Seaweed (Pyropia species) – causes yellow spot disease
- Sea anemones (Exaiptasia pallida) – model system for coral infection
- Brine shrimp (Artemia salina) – experimental host for virulence studies
- Various Mediterranean marine invertebrates
Temperature-Enhanced Virulence and Co-infection Dynamics
Temperature Dependency. V. mediterranei virulence increases significantly at elevated temperatures, making it particularly problematic during warm water conditions and climate change scenarios. This temperature sensitivity makes it a concern for both natural reef systems and heated aquarium environments.
Synergistic Co-infections: V. mediterranei often co-occurs with V. coralliilyticus in coral diseases, and these mixed infections result in enhanced virulence and more severe tissue damage than single-species infections. The bacteria appear to communicate through quorum sensing, increasing their pathogenicity when both species are present.
Multiple Transmission Routes: The pathogen can infect hosts through direct contact with contaminated water, but recent research has revealed that it can also be transmitted through ingestion, bypassing the protective mucus barriers of cnidarians. This discovery has important implications for understanding disease spread in reef systems.
Broad Ecological Impact: Unlike some coral pathogens that are highly host-specific, V. mediterranei demonstrates remarkable versatility, affecting organisms across multiple taxonomic groups including cnidarians, mollusks, and macroalgae, suggesting it may play a key role in marine ecosystem health.
Management and Prevention Strategies
Prevention. Maintain stable water temperatures and avoid thermal stress, as elevated temperatures significantly increase V. mediterranei virulence. Implement strict quarantine protocols for new corals and bivalves, and monitor for early signs of bleaching or tissue necrosis.
Temperature Control. Keep aquarium temperatures stable and avoid sudden increases that could trigger bacterial virulence. During summer months or equipment malfunctions, be especially vigilant for signs of coral bleaching or bivalve mortality.
Early Detection: Watch for coral bleaching, unusual tissue sloughing in invertebrates, or mortality events in bivalves. Species-specific PCR testing can distinguish V. mediterranei from other vibrios when professional diagnosis is needed.
Biocontrol Approaches: Research has shown promise for quorum-sensing disruption and bacteriophage therapy, though these remain experimental. Some beneficial bacteria can reduce V. mediterranei virulence through interference with bacterial communication.
Antibiotic Considerations: Florfenicol has shown some efficacy in treating V. mediterranei infections in bivalves, but complete eradication is difficult and antibiotic resistance may develop. Focus on prevention and environmental management rather than reactive treatment. Important considerations about antibiotic use in reef systems.
V. mediterranei in reef tanks
Prevalence
Looking at how common this pathogen is in other tanks can help you gauge whether finding it in your tank is expected or unusual.
Abundance Distribution
Comparing the levels of this pathogen in your tank with those found in other tanks provides a context for interpreting your test results.
References
Kushmaro, A., et al. (2001). Vibrio shiloi sp. nov., the causative agent of bleaching of the coral Oculina patagonica. International Journal of Systematic and Evolutionary Microbiology, 51(4), 1383-1388. https://doi.org/10.1099/00207713-51-4-1383
Thompson, F.L., et al. (2001). The coral bleaching Vibrio shiloi Kushmaro et al. 2001 is a later synonym of Vibrio mediterranei Pujalte and Garay 1986. Systematic and Applied Microbiology, 24(4), 516-519. https://doi.org/10.1078/0723-2020-00065
Rubio-Portillo, E., et al. (2014). New insights into Oculina patagonica coral diseases and their associated Vibrio spp. communities. The ISME Journal, 8(9), 1794-1807. https://doi.org/10.1038/ismej.2014.33
Rubio-Portillo, E., et al. (2020). Virulence as a Side Effect of Interspecies Interaction in Vibrio Coral Pathogens. mBio, 11(1), e00201-20. https://doi.org/10.1128/mbio.00201-20
Andree, K.B., et al. (2021). Vibrio mediterranei, a potential emerging pathogen of marine fauna: investigation of pathogenicity using a bacterial challenge in Pinna nobilis. Journal of Applied Microbiology, 130(4), 1034-1048. https://doi.org/10.1111/jam.14756
Prado, P., et al. (2020). Presence of Vibrio mediterranei associated to major mortality in stabled individuals of Pinna nobilis L. Aquaculture, 518, 734899. https://doi.org/10.1016/j.aquaculture.2019.734899
Fan, C., et al. (2023). Characterization of Vibrio mediterranei Isolates as Causative Agents of Vibriosis in Marine Bivalves. Microbiology Spectrum, 11(2), e04923-22. https://doi.org/10.1128/spectrum.04923-22
Torres, M., et al. (2018). AHL-lactonase expression in three marine emerging pathogenic Vibrio spp. reduces virulence and mortality in brine shrimp and Manila clam. PLoS ONE, 13(4), e0195176. https://doi.org/10.1371/journal.pone.0195176
Norfolk, W.A., et al. (2023). Coral Disease and Ingestion: Investigating the Role of Heterotrophy in the Transmission of Pathogenic Vibrio spp. Applied and Environmental Microbiology, 89(7), e00187-23. https://doi.org/10.1128/aem.00187-23
Yang, R., et al. (2020). Isolation and identification of Vibrio mediterranei 117-T6 as a pathogen associated with yellow spot disease of Pyropia. Aquaculture, 526, 735372. https://doi.org/10.1016/j.aquaculture.2020.735372