Bacteria classified by scientists as Vibrio are very common in the ocean and some are capable of causing disease in humans. The three major causes of disease are Vibrio cholerae, V. parahaemolyticus and V. vulnificus. Cholera and the so-called non-cholera diseases or vibrioses are reportable to the Centers for Disease Control and Prevention (CDC). All three of these vibrios cause gastroenteritis and wound infections, and in the U.S. the most common agent of disease is V. parahaemolyticus whereas the most lethal is V. vulnificus. Very little is known about the environmental factors that determine the abundance and distribution of these vibrios in their natural environments where they come in contact with humans as a result of swimming or eating undercooked seafood. This research will use the tools of modern molecular biology and chemical oceanography to determine the environmental drivers of vibrio abundance and distribution. Specifically, this project will measure vibrio levels in water, bottom sediment, and oysters in three ecologically and geographically distinct locations ? Chesapeake Bay, Gulf of Mexico and Puget Sound. These data will be correlated with plankton densities and with the following environmental determinants: sea surface temperature, chlorophyll, turbidity, salinity, dissolved organic carbon, primary productivity, particulate organic carbon and nitrogen, dissolved inorganic nutrients, and suspended particulate matter. By linking the in situ measurements with remote sensing imagery, it will be possible to more accurately describe these relationships when real-time environmental sampling is not possible. In addition, this project will host an annual Summer Research Institute to train eight high school students per year in laboratory settings. It is expected that this research will result in a more accurate description of the environmental determinants that influence vibrio abundance and distribution.
Vibrios are naturally occurring bacteria that are found in most salt-containing aquatic environments, such as beaches. Most of these bacteria are harmless, but a small percentage of these populations carry genes that make them potentially harmful for humans and other animals. It is impossible to remove these bacteria from the environment, and one would not want to remove them because they help recycle nutrients in the ocean. The levels of these bacteria increase and decrease throughout the year and around the world, usually in response to temperature; for example, when the beach is warmer, the vibrio levels are higher. Since it is impossible and undesirable to remove these bacteria to minimize human exposures, the best option is to try to predict when vibrio levels will be at high levels and potentially harmful. It is well established that temperature is a predictor of vibrios in general, but the exact contributions of temperature and the relative contributions of temperature plus other factors like salinity are not well understood. It is possible to study the relationship between these bacteria and various environmental parameters in a single geographic location, e.g., the Louisiana Gulf Coast. However, the trends and relationships described in coastal Louisiana may not necessarily apply to coastal Washington or to Bangladesh. To maximize the understanding of how vibrios respond to changing environmental factors, it is necessary to maximize the geographic regions in which these questions are asked. This project measured vibrio levels in three different sample types (water, oysters, and sediment) in four different geographic locations (the coasts of Washington, Louisiana, Mississippi, and Maryland), and it also collected concurrent data on temperature, salinity, dissolved organic carbon, suspended particulate matter, and chlorophyll. This research found that all five parameters were correlated with vibrios in some way. For example, temperature accounted for 11 to 14% of the abundance of at least one of the four vibrio populations targeted [total Vibrio parahaemolyticus, thermostable direct hemolysin (tdh) containing V. parahaemolyticus, tdh-related hemolysin (trh) containing V. parahaemolyticus, or total Vibrio vulnificus]. By examining the combinations of parameters that correlate with number of vibrios, it is possible to predict when environmental conditions will be vibrio-favorable and, therefore, potentially dangerous for humans, particularly immunocompromised consumers of raw oysters. By determining the precise contribution of each of these parameters, it is possible to detect and predict those conditions by using satellite remote sensing, very much akin to weather prediction. Thus, the results of this research show how vibrios interact with their environment, allowing future studies to build on these findings and predict conditions conducive to outbreaks of diseases caused by vibrios, thereby saving lives.
