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

## TL;DR

This study examines the presence and diversity of harmful Vibrio bacteria in Lake Pontchartrain, finding higher concentrations in summer and identifying multiple pathogenic species.

## Contribution

The study provides the first detailed spatiotemporal analysis of multiple pathogenic Vibrio species in Lake Pontchartrain using culture and molecular methods.

## Key findings

- Vibrio concentrations were significantly higher in summer (5.2 × 10⁴ CFU/L) compared to winter (3.2 × 10³ CFU/L).
- Water temperature and salinity were significant predictors of Vibrio abundance.
- 41 Vibrio species were identified, with V. cholerae, V. vulnificus, and V. mimicus being most prevalent.

## Abstract

Although several studies have reported the occurrence of Vibrio species in the Gulf Coast of the United States (U.S.), relatively little is known about the distribution of multiple pathogenic Vibrio species in Lake Pontchartrain in Louisiana, the second largest estuary in the U.S. In this study, bacterial culture, quantitative PCR (qPCR), and long-read sequencing methods were used to assess the prevalence, distribution, and diversity of Vibrio species in this recreational estuary. Water samples (n = 101) were collected from nine sites over 12 months from November 2023 to November 2024. During the summer months (June, July, and August), the average Vibrio species concentration was 5.2 × 104 CFU/L. While in the winter months (December, January, and February), the average Vibrio concentration was 3.2 × 103 CFU/L. Likewise, the temperature differed between summer and winter, with the average water temperatures being 30.39°C and 14.45°C, respectively. Linear modeling showed water temperature and salinity were found to be significant (P < 0.05) predictors of Vibrio concentrations from both culture methods and qPCR. Precipitation was found to be significantly associated with total culturable Vibrio abundance. The toxR genes of Vibrio cholerae, Vibrio vulnificus, and Vibrio parahaemolyticus persisted throughout the year. Bacterial isolate sequencing revealed 41 Vibrio species in the estuary, with V. cholerae, V. vulnificus, and V. mimicus making up the largest proportion of the community. Genes specific to the O139 serotype of V. cholerae were also identified in pooled isolate samples. Additionally, the V. vulnificus hemolysin gene was detected in 84.2% of samples throughout the year, with higher concentrations in the summer and early fall months. Overall, diverse Vibrio species were detected in this recreational estuary under a broad range of environmental conditions, underscoring the value of using both culture- and molecular-based methods to surveil these pathogens of public health concern.

Globally, 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 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 provides new information on the prevalence and diversity of pathogenic Vibrio spp. at recreational sites along the shore of Lake Pontchartrain. The findings underscore the need for regular monitoring of Vibrio levels in coastal water during the recreational season for early warning and educating the public on the potential exposure risks.