Biology subjects

Samsing, F.

Publications and source records attributed to Samsing, F..

3 recordsLinked to original sources

bioRxiv2026

A new lineage of Ranavirus micropterus1 infects ornamental wrasses from the Great Barrier Reef and causes severe disease in captivity

The Great Barrier Reef (GBR) supports remarkable vertebrate diversity but is among the most fragile ecosystems globally, and diseases affecting reef fishes remain poorly understood. We employed traditional veterinary diagnostic techniques and metatranscriptomics to investigate a disease outbreak with 100% mortality in captive wrasses (Macropharyngodon choati) from the GBR. Histopathology revealed multifocal necrosis of renal tubules, and cytopathic effect was observed in bluegill fry cell lines. A novel ranavirus isolate, Macropharyngodon choati ranavirus (McRV), was identified at exceptionally high transcript abundance across different host tissues, alongside strong expression of host genes linked to cellular stress and immune function. Phylogenetic analysis placed McRV in a distinct clade of wrasse ranaviruses, clustering with a virus previously identified on the GBR, suggesting that wild wrasses serve as natural hosts. These data emphasise the need for enhanced pathogen monitoring in marine wildlife increasingly threatened by anthropogenic change.

microbiology↗

bioRxiv2025

Vibrio harveyi plasmids as drivers of virulence in barramundi (Lates calcarifer)?

Vibrio species are an emerging public and animal health risk in marine environments and the opportunistic bacterial pathogen Vibrio harveyi is a major disease risk for tropical aquaculture. Current understanding of virulence in V. harveyi is limited by strain-specific variability and complex host-pathogen dynamics. This study sought to integrate genomic investigation, phenotypic characterisation and in vivo challenge trials in barramundi (Lates calcarifer) to increase our understanding of V. harveyi virulence. We identified two hypervirulent isolates, Vh-14 and Vh-15 that caused 100% mortality in fish within 48 hours, and that were phenotypically and genotypically distinct from other V. harveyi isolates. Virulent isolates contained multiple plasmids, including a 105,412 bp conjugative plasmid with type III secretion system genes originally identified in Yersinia pestis. The emergence of this hypervirulent plasmid-mediated patho-variant poses a potential threat to the sustainable production of marine finfish in Southeast Asia, the Mediterranean and Australia. In addition, we observed an effect of temperature on phenotypic indicators of virulence with an increase in activity at 28{degrees}C and 34{degrees}C compared to 22{degrees}C. This suggests that temperature fluctuations associated with climate change may act as a stressor on bacteria, increasing virulence gene secretion and host adaptation. Our results utilising a myriad of technologies and tools, highlights the importance of a holistic view to virulence characterisation.

microbiology↗

bioRxiv2024

Understanding the Transfer and Persistence of Antimicrobial Resistance in Aquaculture Using a Model Teleost Gut System

The development, progression, and dissemination of antimicrobial resistance (AMR) is determined by interlinked human, animal, and environmental drivers, posing severe risks to human health. Conjugative plasmid transfer drives the rapid dissemination of AMR among bacteria. Besides antibiotic judicious use and implementation of antibiotic stewardship programs, mitigating antibiotic resistance spread requires an understanding of the dynamics of AMR transfer among microbial communities, as well as the role of various microbial taxa as potential reservoirs that promote long term AMR persistence. Here, we employed Hi-C, a high-throughput, culture-free technique, combined with qPCR, to monitor carriage and transfer of a multidrug-resistant plasmid within an Atlantic salmon in vitro gut model during florfenicol treatment, a benzenesulfonyl antibiotic widely deployed in fin-fish aquaculture. Microbial communities from the pyloric ceaca of three healthy adult farmed salmon were inoculated into three bioreactors developed for the SalmoSim gut system. The model system was then inoculated with an Escherichia coli strain ATCC 25922 carrying plasmid pM07-1 and treated with florfenicol at a concentration of 150 mg/L fish feed media for five days prior to a washout/recovery phase. Hi-C and metagenomic sequencing identified numerous transfer events, including to gram-negative and gram-positive taxa and, crucially, continuing transfer and persistence of the plasmid once florfenicol treatment had been withdrawn. Our findings highlight the role of commensal teleost gut flora as a reservoir for AMR, and our system provides a model to study how different treatment regimes and interventions may be deployed to mitigate AMR persistence.

microbiology↗