Author: Sein Hwang
Hwang, Sein, 2024 Assessing Antibiotic Resistance in the Skin Microbiome of Elasmobranchs: A Comparative Analysis , Flinders University, College of Medicine and Public Health
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Antimicrobial resistance is a growing global health concern, and a One Health Perspective is being used to tackle the problem. Anthropogenic pollutants, such as antibiotics from runoff, contribute to and accelerate the spread of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) in marine ecosystems. Elasmobranchs, as top predators in marine ecosystems, may be good bioindicators for detecting environmental contamination. My research investigates the diversity and antibiotic resistance patterns of skin microbiomes in six elasmobranch species (sharks, rays, and skates) from the Gulf St. Vincent in Australia, focusing on their role in marine antimicrobial resistance (AMR) in the marine environment. Their skin microbiomes, composed of bacteria such as Pseudoalteromonas and Psychrobacter, were examined to assess their antibiotic resistance patterns and the presence of ARGs. The study involved:
• Culturing microbes from elasmobranchs' skin.
• Performing antimicrobial susceptibility testing on eight common antibiotics.
• Sequencing microbial genomes to identify ARGs.
Results revealed that Pseudoalteromonas and Psychrobacter were predominant across most hosts, indicating their potential adaptation to the skin environment. Significant resistance to Penicillin was observed in 84 % of the microbes tested, while there were low resistance rates for Sulphafurazole, Chloramphenicol, Tetracycline, and Erythromycin. Whole genome sequencing of selected microbes via the MinION device revealed several ARGs, including those for efflux pumps and beta-lactamases. However, inconsistencies existed between 'Specialty Genes' ARGs identified by the BV-BRC annotation platform (2024) and the resistance identified from antimicrobial susceptibility tests. These inconsistencies highlight the complexity of resistance mechanisms and the need to integrate genomic and phenotypic data.
In conclusion, my study highlights the diversity of microbes and antibiotic resistance patterns in the skin microbiome of six elasmobranch species, with Pseudoalteromonas and Psychrobacter being predominant. Apart from resistance to Penicillin, most elasmobranch microbes were sensitive to the antibiotics, suggesting a limited flow of ARGs into the shark microbiome. Therefore, sharks are not currently a mechanism of moving antibiotics in the marine environment in these locations.
Only eight cultured microbes were fully sequenced, while the majority relied on 16S rRNA sequencing, limiting a comprehensive understanding of microbial genomes. Inconsistencies between potential antibiotic resistance genes identified by BV-BRC analysis and antimicrobial susceptibility test results underscore the complexity of resistance mechanisms. Further research, including complete genome sequencing of more microbial samples, is essential to improve the understanding of the antibiotic resistance genes and microbial adaptation in these marine organisms. The ecological importance of elasmobranchs and their role in maintaining marine biodiversity, as well as understanding their skin microbiomes and associated resistance patterns, provides a valuable perspective on the impact of AMR in marine ecosystems.
Keywords: Antimicrobial Resistance (AMR), Elasmobranch, Skin Microbiome, Antibiotic Resistance Genes (ARGs), Whole Genome Sequencing
Subject: Biotechnology thesis
Thesis type: Masters
Completed: 2024
School: College of Medicine and Public Health
Supervisor: Elizabeth Dinsdale