Rapid and accurate detection of bacterial diseases is critical to maintaining healthy stock in commercial warmwater marine finfish aquaculture. Intensive rearing conditions and environmental factors (i.e., suboptimal stocking density, water temperature, salinity) can induce stress and increase fish susceptibility to infection by ubiquitous Vibrio species that are opportunistically pathogenic. This study focuses on developing molecular techniques for use in an aquaculture facility to detect the presence of Vibrio harveyi. We compare the effectiveness of two different screening methods for V. harveyi: 1) a portable PCR system, miniPCR® mini16 thermal cycler (Cambridge, MA) under farm conditions, and 2) a benchtop PCR system, EDVOTEK EdvoCycler Jr.® (Washington, DC) in a laboratory setting. Additionally, we assess the direct input of unpurified samples versus purified DNA as template for PCR.
Biofilm samples were collected from aquaculture tanks housing red drum (Sciaenops ocellatus) at FAU Harbor Branch Oceanographic Institute. Both crude swab samples and extracted DNA samples were tested on the mini16 in the field and the Edvotek thermocycler in the lab. PCR was conducted with Platinum™ Direct PCR Universal Master Mix (Thermo Fisher Scientific, Inc., Waltham, MA) to amplify a 601 bp DNA fragment of the rpoB gene in Vibrio harveyi. A pure V. harveyi culture (ATCC 14126) served as the positive control. PCR products were visualized via gel electrophoresis to compare the DNA band size and intensity among samples. We expect to successfully employ both methods for Vibrio harveyi detection, with potential differences in the quality of PCR results between the direct input of unpurified samples and purified DNA.
This study aims to provide insights into the feasibility of rapid, field-based disease detection methods in aquaculture, offering a comparison of the efficacy between field-deployable and traditional lab-based PCR techniques. These results could streamline diagnostic workflows and support better management practices in warmwater marine finfish aquaculture. Our overall goal is to develop rapid and early disease diagnostic tools that can be easily accessible to producers and veterinarians to assess fish health at a commercial production level.