Spatiotemporal distribution and species diversity of pathogenic Vibrios in estuarine recreational waters of southeast Louisiana

Abstract

Vibrio bacteria occur naturally in brackish water and can cause illnesses through recreational water exposure. Vibrio infections have shown a notable increase in recent years worldwide. In this study, bacterial culture and molecular methods were used to assess the prevalence and diversity of Vibrio species in the estuary of Lake Pontchartrain, the second largest inland brackish body in the United States. Water samples (n= 101) were collected from 9 recreational sites from November 2023 to November 2024. During the summer months (June, July, and August), the average Vibrio species. concentration was 5.2 x 104 colony-forming unit (CFU)/L. While in the winter months (December, January, and February), the average Vibrio spp. concentration was 3.2 x 103 CFU/L. Likewise, the temperature differed between summer and winter, with the average water temperatures being 30.39 {degrees}C and 14.45 {degrees}C, respectively. Linear modelling showed water temperature and salinity were found to be significant (p < 0.05) predictors of Vibrio concentrations from both culture methods and quantitative PCR, while precipitations were only significant for bacterial culture. The toxR genes of Vibrio cholerae, Vibrio vulnificus, and Vibrio parahaemolyticus persisted throughout the year, and 14.8% (n=9) of sequenced samples were identified as the O139 serotype of V. cholerae. Bacterial isolate sequencing revealed more than 100 Vibrio species in the lake with V. cholerae, V. vulnificus, and V. mimicus making up the largest proportion of the community. Continuous environmental monitoring of Vibrio is warranted in informing public health preparedness and expanding our understanding of the ecology of this pathogen. ImportanceGlobally, the diverse bacterial genus Vibrio is an important group of pathogens in coastal water environments. These bacteria are responsible for waterborne and seafood-borne illnesses as well as skin infections from recreational activities. Despite the rising incidence of Vibrio infections, routine monitoring of Vibrio species (spp.) in the environment remains limited. This gap hinders our understanding of their distribution, especially in estuarine areas, and potential public health risks linked to recreational activities. This study employed multiple techniques including bacterial culture, quantitative PCR, and genome sequencing to assess the prevalence, distribution, and diversity of Vibrios in the estuary. This study shows that Vibrio cholerae were prevalent in recreational water of a non-endemic region. The findings underscore the need for regular monitoring of Vibrio levels in recreational water and educating the public on the risks.