Emerging Vibrio harveyi and Vibrio campbellii pathogens in Georgia Waters

Cameron Brown, Georgia College & State University


In the face of global warming and ocean acidification, waterborne pathogens are geographically expanding and rapidly evolving. The Vibrio genus contains a number of pathogens of humans and aquatic animals, many of which benefit from elevated temperatures and low pH conditions. Vibrio harveyi and Vibrio campbellii belong to the Harveyi clade and are barely distinguishable upon their genetic make-up. Natively found in warm waters of Asia and South America, these species are well-established pathogens that infect fish, shrimp, and mollusks. Due to climate change, the Southeastern United States is potentially becoming an accommodating environment for these pathogens, however this has never been previously documented. In addition to using selective growth media for definitive pathogen detection, V. harveyi and V. campbellii-specific virulence genes, including toxR, luxR, vhh, vhh(a), srp, vhp, and rpoA, have been chosen for quantitative PCR analysis of environmental samples. Sediment and water were monitored for their presence and concentration at three sites around Townsend, GA. In summer 2022 monitoring, all seven genes were detected but their profiles and concentrations varied between sites, media, and sampling events. In water, toxR, luxR, srp, and rpoA were detected in 83% of the sites, and vhh(a), vhp, and vhh were detected in 100% with average gene copy concentrations from 10^2 to 10^8. In sediment, srp, vhh(a), and rpoA were detected in 83% of the sites and toxR, luxR, vhp, and vhh were detected in 100% of the sites with copy numbers from 10^1 to 10^9. These results evidenced that V. harveyi and V. campbellii inhabit Georgia coastal waters in high numbers. Additional data obtained in a supplemental study suggested their presence in oysters and clams. They also evidenced that not all previously published target genes are suitable for detection of these pathogens.