Pseudomonas putida

Sea Cucumber Disease Linked to Multidrug-Resistant Bacterial Strain

Emerging research links sea cucumber skin ulceration disease (SUD), a significant threat to aquaculture, to a virulent strain of *Pseudomonas putida*.

September 24, 20265 min readFrontiers in Marine Science | New and Recent Articles

Sea Cucumber Disease Linked to Multidrug-Resistant Bacterial Strain

Our take

## Our Take: Unraveling the Threat of Sea Cucumber Disease – A Genomic Perspective

The escalating threat to sea cucumber aquaculture, particularly *Apostichopus japonicus*, demands urgent attention, and this recent study provides a critical foundation for understanding and mitigating the devastating impacts of Skin Ulceration Disease (SUD). Sea cucumbers are increasingly important globally for both their ecological role in seabed health and their significant economic value, particularly in East Asia. As highlighted in Ocean-Based Solutions for Food Security, sustainable aquaculture is vital for meeting growing food demands while minimizing environmental impact, and SUD directly undermines this potential. This new research, meticulously detailing the genomic characterization of *Pseudomonas putida* as the causative agent, moves beyond simple identification to reveal the intricate mechanisms driving the disease’s virulence and multidrug resistance. The combination of phenotypic analysis, whole-genome sequencing, and pathogenicity assays establishes a robust genetic framework for understanding SUD pathogenesis, a significant step forward from previous, more limited investigations. The identification of virulence-associated genes related to motility, immune evasion, and iron acquisition offers targeted avenues for future research and intervention strategies. Furthermore, the discovery of multidrug resistance within this *P. putida* strain underscores the growing global challenge of antimicrobial resistance in aquatic environments, as discussed in Antimicrobial Resistance in Aquaculture.

The study's emphasis on environmental factors – specifically, optimal bacterial growth at 30.22°C and low salinity (10.78‰) – is particularly insightful. It suggests that climate change-induced shifts in ocean conditions could exacerbate SUD outbreaks, creating a feedback loop where warming waters and altered salinity levels promote bacterial proliferation and disease spread. This observation highlights the interconnectedness of ocean health, climate change, and aquaculture sustainability. The researchers’ proposed framework for therapeutic management – incorporating environmental monitoring, targeted antibiotic selection (prioritizing cephalosporins), and exploration of phage therapy – reflects a pragmatic and forward-thinking approach. While phage therapy remains a developing field, its potential to circumvent antibiotic resistance offers a promising long-term solution. The comprehensive resistome analysis, identifying key resistance genes like *mexw*, *mexb*, and *adeF*, provides invaluable data for predicting antibiotic efficacy and guiding treatment strategies, a crucial element in managing this emerging threat. It’s also worth noting the study’s contribution in providing the “first complete whole-genome and genetic blueprint” of this *P. putida* strain – a foundational resource for the broader scientific community to build upon.

Beyond the immediate implications for sea cucumber aquaculture, this research contributes to a broader understanding of bacterial pathogenesis in marine environments. The detailed characterization of virulence factors and antibiotic resistance mechanisms in *P. putida* offers valuable insights applicable to other bacterial diseases affecting marine organisms. The integrated data ecosystem approach, combining phenotypic and genomic data, exemplifies a modern, data-driven approach to disease management. This methodology underscores the power of longitudinal data collection and analysis in identifying and predicting disease outbreaks. The study’s rigorous methodology, including ANI and dDDH analyses to confirm species classification and probit analysis for LD50 determination, reinforces the scientific credibility of its findings, ensuring that the insights derived are robust and reliable. The validation process employed is crucial for establishing the accuracy of the identification and pathogenicity assessments, which is vital for informing effective intervention strategies.

Looking ahead, the most pressing question revolves around the practical implementation of the researchers’ recommendations. Can environmental monitoring systems be effectively deployed and integrated into existing aquaculture management practices to provide early warning of potential SUD outbreaks? Furthermore, how can phage therapy be scaled up and adapted for use in sea cucumber aquaculture, ensuring both efficacy and safety? The study’s findings offer a crucial roadmap, but the translation of these insights into tangible solutions will require collaborative efforts between researchers, policymakers, and aquaculture stakeholders. The Future of Sustainable Aquaculture depends on our ability to proactively address emerging threats like SUD and to foster resilient, data-driven aquaculture practices.

Skin ulceration disease (SUD) increasingly threatens sea cucumber (Apostichopus japonicus) aquaculture. In this study, we isolated and characterized the associated pathogen from diseased sea cucumbers using phenotypic and whole-genome analyses. Naturally infected individuals exhibited white ulcer spots, evisceration, and tissue disintegration. Multiple strains were isolated and identified as Pseudomonas putida using ANI and dDDH, supported by 16S rRNA NJ phylogenetic analysis. One representative strain, designated WL2, was selected for further analysis, with its species classification confirmed by Non-Redundant Protein database (NR) annotation, bacterial morphology observation, and biochemical identification. The pathogenicity of WL2 was demonstrated by a challenge assay, which determined a median lethal dose (LD50) of 2.54 × 107 CFU/mL using probit analysis, indicating high virulence. Furthermore, whole-genome sequencing was used to elucidate the mechanistic basis of pathogenicity and identify a suite of virulence-associated genes mainly involved in motility (flagella and type IV pili), immune evasion (LPS, LOS, and alginate), and iron acquisition (pyoverdine), providing a genetic framework for understanding SUD pathogenesis. Antibiotic susceptibility testing showed multidrug resistance to 19 antibiotics and susceptibility to cefotaxime, ceftriaxone, imipenem, and aztreonam; the resistance phenotype was supported by a corresponding resistome, including mexw, mexb, mexf, baca, and adeF. The observed optimal growth at 30.22 °C and low salinity (10.78‰) raises the testable hypothesis that outbreak risk may be elevated when environmental conditions favor bacterial proliferation. For therapeutic management, we propose a framework incorporating environmental monitoring (temperature, salinity, pH), targeted antibiotic selection (prioritizing cephalosporins), and long-term alternatives such as phage therapy. To our knowledge, this study provides the first complete whole-genome and genetic blueprint of P. putida associated with SUD in sea cucumbers, providing actionable insights for SUD control.

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