AUTHOR=Kaimal Sindhu , Farmer Bradley D. , Renukdas Nilima N. , Abdelrahman Hisham A. , Kelly Anita M. 

TITLE=Evaluating Stress-Mediated Microbial Pathogenesis in Golden Shiners, Notemigonus crysoleucas

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.886480

DOI=10.3389/fphys.2022.886480

ISSN=1664-042X

ABSTRACT=<p><italic>Flavobacterium covae</italic> (columnaris) is a microbial pathogen of the Golden Shiner (<italic>Notemigonus crysoleucas</italic>), a principal bait species. We investigated the effects of density and water temperature on the survival of fish subjected to a columnaris challenge and whether flow cytometry (FCM) could be a fast and reliable method to distinguish and enumerate <italic>F. covae</italic> populations from water and fish in experimental tanks. Juvenile Golden Shiners averaging 2.62 (±0.78 S.D.) g (negative for <italic>F. covae</italic>) were used in simultaneous trials at 22°C and 28°C in two ultra-low flow-through systems: each consisting of four treatments and five replicates per treatment. Treatments were fish stocked at either 600 fish/m<sup>3</sup> or 2,400 fish/m<sup>3</sup> and either challenged with <italic>F. covae</italic> or not; survival was observed for 48 h after challenge. Samples of water and fish tissue were obtained for FCM enumerations and validation by qPCR. No significant differences in survival were recorded between density treatments; however, high temperature and columnaris challenge treatments showed significantly higher mortality. Bacterial enumeration (number/mL) by FCM highly correlated with bacterial counts <italic>r</italic> = 0.81 (<italic>p</italic> = 0.001) in the water samples. Higher water temperatures may have increased columnaris infections and mortality in Golden Shiners. Flow cytometry is a reliable method of enumerating <italic>F. covae</italic> from experimental tank water samples.</p>