Temporal and Spatial Variability in Culturable Pathogenic Vibrio spp. in Lake Pontchartrain, Louisiana, following Hurricanes Katrina and Rita

Abstract

We investigated the abundance, distribution, and virulence gene content of Vibrio cholerae, V. parahaemolyticus, and V. vulnificus in the waters of southern Lake Pontchartrain in Louisiana on four occasions from October 2005 to September 2006, using selective cultivation and molecular assays. The three targeted pathogenic vibrios were generally below the detection level in January 2006, when the water was cold (13°C), and most abundant in September 2006, when the lake water was warmest (30°C). The maximum values for these species were higher than reported previously for the lake by severalfold to orders of magnitude. The only variable consistently correlated with total vibrio abundance within a single sampling was distance from shore (P ‫؍‬ 0.000). Multiple linear regression of the entire data set revealed that distance from shore, temperature, and turbidity together explained 82.1% of the variability in total vibrio CFU. The log-transformed mean abundance of V. vulnificus CFU in the lake was significantly correlated with temperature (P ‫؍‬ 0.014), but not salinity (P ‫؍‬ 0.625). Virulence-associated genes of V. cholerae (ctx) and V. parahaemolyticus (trh and tdh) were not detected in any isolates of these species (n ‫؍‬ 128 and n ‫؍‬ 20, respectively). In contrast, 16S rRNA typing of V. vulnificus (n ‫؍‬ 298) revealed the presence of both environmental (type A) and clinical (type B) strains. The percentage of the B-type V. vulnificus was significantly higher in the lake in October 2005 (35.8% of the total) than at other sampling times (P < 0.004), consistent with the view that these strains represent distinct ecotypes.

Ecology of Vibrio parahaemolyticus and Vibrio vulnificus in the Coastal and Estuarine Waters of Louisiana, Maryland, Mississippi, and Washington (United States)

“…This is consistent with the significant relationships previously identified between turbidity and V. parahaemolyticus abundance (30,31,33,47,54). A positive association with turbidity is consistent with expectations because vibrios, like many other bacteria, are frequently attached when in the aquatic environment (16).…”

“…Regression models incorporating an interaction between temperature and salinity were explored but did not significantly improve overall goodness-of-fit or otherwise provide an interpretation for the unexpected findings. Some studies have identified a significant relationship between vibrios and salinity (6,12,30,31,60,69,79), while others did not (47,60,66,68), so the relationship with salinity may be variable and complex. For example, Griffitt and Grimes (unpublished data) found that large salinity shifts, as seen during the opening of the Louisiana Bonnet Carré Spillway following the Mississippi River floods of 2011, can cause detectable and significant change in the relative numbers of pathogenic vibrios.…”

Influence of Environmental Factors onVibriospp. in Coastal Ecosystems

“…Positive relationships have been described between temperature and total vibrios in the waters of Germany (58,59), North Carolina (31,55,60,61), the country of Georgia (62), the state of Georgia (63), Italy (64,65), South Africa (66), and Germany (47). Interestingly, negative correlations have also been described between temperature and total vibrios in the waters of India (46,67) and Louisiana (68). Temperature has also been positively correlated to total vibrios in mussels (59) and sediment (47,64,69).…”

Interactions ofVibriospp. with Zooplankton

“…Strong correlations between the occurrence of Vibrio spp. and temperature, salinity, chlorophyll a, rainfall, and dissolved oxygen have been reported repeatedly (51,52,53,54,55,56,57), and such measures, therefore, have significant potential for the use as early warning and monitoring systems to predict outbreaks of cholera.…”