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Aims: To understand spatial–temporal distribution of Vibrio parahaemolyticus and Vibrio vulnificus in triploid Crassostrea virginica in off‐bottom aquaculture. Methods and Results: Oysters, sediments and water were seasonally collected in Georgia, USA. V. parahaemolyticus and V. vulnificus were quantified with tlh/tdh/trh and vvhA genes, respectively. No tdh/trh genes were detected. Highest concentrations of tlh gene were observed in summer sediments > oysters > water (105/g, 104/g, 103/ml). VvhA concentrations were similar in sediments and oysters but never exceeded ≥3 × 101/ml in water. Concentrations of tlh and vvhA genes correlated to temperature and turbidity, respectively, which along with their different spatial distribution indicated different environmental drivers. In oysters, ratios of the tlh and vvhA to 16S rRNA gene have increased from 0 to 10−1 and 10−2 in summer, while these ratios in water and sediments were lower by 2–3 orders of magnitude. Conclusions: Dynamics of tlh and vvhA concentrations and abundances suggested enrichment of V. parahaemolyticus and V. vulnificus by off‐bottom triploid oysters in summer resulting in their abundance by far exceeding that in water. Significance and Impact of the Study: This first report on enrichment of Vibrio pathogens in triploid oysters with no direct contact to sediments reveals a threat to human health suggesting their monitoring in triploid off‐bottom C. virginica aquaculture. [ABSTRACT FROM AUTHOR]

Abstract: The occurrence of tetracycline resistance (TRG) and integrase (INT) genes were monitored in Crassostrea virginica oyster reefs of three pristine creeks (SINERR, Georgia, USA). Their profiles revealed 85% similarity with the TRG/INT profiles observed in the adjacent to the SINERR and contaminated Altamaha River estuary (Barkovskii et al., 2010). The TRG/INT spectra and incidence frequencies corresponded to the source of oceanic input and to run-offs from creeks’ watersheds. The highest incidence frequencies and concentrations were observed in oysters. TRG/INT incidences correlated positively (Spearman Rank=0.88), and negatively correlated (−0.63 to −0.79) with creek salinity, conductivity, dissolved solids, and temperature. Coliform incidence positively correlated with temperature, and not with the TRG/INT incidence. The Altamaha River estuary was the primary TRG/INT source for the reefs with contributions from creek’s watersheds. TRG/INT were carried by non-coliforms with a preference for low-to-temperate thermohaline environments coupled with bioaccumulation by oysters. [Copyright &y& Elsevier]