Abstract:
Pearl oyster farming is a critical industry in marine aquaculture, relying heavily on the surgical implantation of a nucleus and mantle tissue to induce pearl formation. However, this delicate process comes with the risk of post-surgical infections, which can compromise oyster health, survival rates, and the quality of pearls produced. To mitigate the risk of bacterial infection, antibiotics such as oxytetracycline, chloramphenicol, and kanamycin have been used in aquaculture systems. Despite their effectiveness in infection control, the widespread and often indiscriminate use of antibiotics has led to the alarming rise of antimicrobial resistance (AMR), creating both ecological and public health threats. The aquaculture sector, therefore, urgently requires sustainable, effective alternatives to antibiotics, especially in environmentally sensitive systems like pearl oyster farms.
This study aims to present an innovative solution to this growing challenge by exploring the use of naturally derived bacteriophages—viruses that specifically infect and lyse bacteria—as a post-operative treatment in marine pearl oyster culture. Bacteriophages, in contrast to broad-spectrum antibiotics, offer a highly targeted and eco-friendly alternative, with minimal risk of disrupting non-target microbiota and no harmful residue left in the environment. In this research, bacteriophages were extracted from pristine seawater collected from an uncontaminated coastal region of the Andaman Sea, known for its abundant and diverse marine microbial population. The primary objective was to determine the efficacy of these native bacteriophages in promoting post-surgical healing and preventing bacterial infections in the pearl oysters Pinctada margaritifera and Pteria penguin, which are native to the Andaman Sea.
The experimental design involved a randomized control trial with 400 oysters subjected to surgical implantation of nucleus and graft tissue. The oysters were divided into three groups: a phage-treated group (n=150), an antibiotic-treated group (n=150), and a control group (n=100). The phage-treated oysters were immersed in bacteriophage-enriched seawater for 72 hours, while the antibiotic-treated oysters were exposed to oxytetracycline at 1.5 ppm for the same duration. The control group was maintained in untreated filtered seawater. Several parameters were monitored, including mortality rates, wound healing times, shell closure rates, nacre deposition quality, microbial load at the wound site, and histological tissue analysis.
The results revealed striking differences between the treatment groups. The phage-treated oysters exhibited significantly faster wound healing, with recovery times ranging between 48 and 72 hours, compared to the antibiotic-treated group, which took 72 to 96 hours to recover. Mortality in the phage-treated group was markedly lower (5%) compared to the antibiotic-treated group (12%) and control group (18%). Histological analysis further corroborated these findings, showing reduced inflammation and superior tissue regeneration in the phage-treated oysters. The microbial analysis revealed that phage therapy effectively reduced pathogenic Vibrio spp., particularly Vibrio harveyi and Vibrio alginolyticus, without negatively affecting the beneficial microbial communities essential for oyster health.
One of the key advantages of phage therapy was its specificity—phages only targeted harmful bacteria while leaving beneficial microbes intact. Furthermore, phage therapy demonstrated the ability to self-replicate at the infection site, providing sustained antimicrobial activity without the environmental persistence associated with antibiotic residues. This self-amplifying property ensures a long-lasting effect, making phages an ideal candidate for sustainable aquaculture management.
In contrast, the antibiotic-treated oysters showed moderate healing times and higher levels of pathogen load. This inefficiency could be attributed to the emergence of antibiotic-resistant bacterial strains within the aquaculture system. Additionally, the use of antibiotics raised concerns about potential residual contamination in the final product, which can pose risks to both consumer health and the broader environment.
This study highlights the potential of bacteriophage therapy as a sustainable, environmentally friendly alternative to antibiotics in pearl oyster farming. By reducing mortality rates, accelerating wound healing, and enhancing nacre quality, phage therapy offers a compelling solution to some of the most pressing challenges in the aquaculture industry. Moreover, the study demonstrates the practicality of phage-based interventions, which can be seamlessly integrated into existing pearl farming practices without the need for major infrastructure changes or new regulatory approvals.
In addition to offering a promising alternative to antibiotics in pearl oyster aquaculture, this research opens up avenues for further investigation into the use of phage therapy in other bivalve species and aquaculture systems worldwide. The findings of this study also contribute to the global effort to combat AMR, providing a model for responsible and sustainable aquaculture that aligns with the increasing demand for antibiotic-free seafood production.
Keywords:
Phage therapy, pearl oysters, antimicrobial resistance, sustainable aquaculture, Pinctada margaritifera, Pteria penguin, post-surgical care, marine biotechnology, Vibrio pathogens, Andaman Sea, environmental sustainability