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  • Genetic and population structure analysis of clinical and environmental Vibrio parahaemolyticus strains


Northwest Fisheries Science Center (NWFSC) Office of the Science Director


Vibrio population structure
Genetic and population structure analysis of clinical and environmental Vibrio parahaemolyticus strains
Vibrio parahaemolyticus (Vp) is a marine bacterium capable of causing severe gastroenteritis in humans, usually through the consumption of raw shellfish. Before 1995, Vp-vibriosis was sporadic world-wide and caused by a relatively heterogeneous population of the bacterium. Since then, outbreaks have become more epidemic, with foci of infections traced to seafood harvested from single or geographically-linked sites. While initial outbreaks in Asia (and later in South America and the U.S. Gulf Coast region) have been attributed to a single serotypically-related pandemic clonal complex, other serotypes have been implicated in distinct geographical areas, including the Pacific Northwest and Alaska in the U.S.

Current risk assessment models are based on the presence of the virulence-associated genes tdh and trh, yet illnesses have been attributed to tdh- and/or trh- isolates. Previous phylogenetic studies have shown that Vp, like most Vibrio spp., is a genetically diverse species, and as yet there has been no definitive conclusion as to what genes are essential for virulence. Using phenotypic, genetic, and genomic comparison methods such as Multi-Locus Sequence Typing (MLST), we are examining the hypothesis that a set of highly-virulent clones of Vp with increased pathogenic potential have recently emerged in the PNW, and determining whether the emergence can be correlated with specific environmental parameters. MLST and other genotyping analyses of clinical and environmental Vp isolates from PNW sources demonstrate the extensive patterns of diversity as seen elsewhere. However, the majority of PNW strains obtained from human infections form a distinct clonal complex separate from most environmental isolates. Interestingly, many environmental isolates obtained from PNW sources are phylogenetically related to the pandemic clonal complex, but this group has not been associated with clinical infections in the region.

Research Themes

Sustainable, safe and secure seafood for healthy populations and vibrant communities
Effective fisheries management provides economic opportunities and ensures the long-term sustainability of fisheries and the habitats on which they depend. The NWFSC seeks to improve the quality and quantity of data used in stock assessments, the methods for assessing stocks and ecosystem sustainability within the context of human modification of the environment. The NWFSC also provides state-of-the-art science and technology to support aquaculture while protecting and maintaining ecosystem health. Further, pathogens, toxins from harmful algal blooms (HABs), chemical contaminants and other stressors of marine ecosystems pose significant risks to health of both seafood resources and to humans. The NWFSC focuses on research to improve understanding of those risks, how to forecast them, and identify means to mitigate their impacts.

Research Foci

Provide scientific support to ensure safe seafood for healthier populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants, and biotoxins
The availability of nutritious and safe seafood from marine ecosystems and aquaculture are essential to maintain and maximize human health. Even though fish are known to have a variety of health benefits, some seafood (wild or farmed) may contain levels of toxic compounds (e.g., chemical contaminants, pathogens, biotoxins) from a variety of human-related and natural sources that can pose health risks to humans, especially for those groups with high rates of seafood consumption. The development of novel methods and technologies to assess seafood safety and biological effects of these toxic compounds remains a priority for commercial, subsistence and recreational consumption of seafood. For example, several species (e.g., zebrafish, sea lions, shellfish) are excellent indicators of environmental stress and potential health threats to marine species and humans. These species can serve as informative animal models for investigations of the mechanisms of toxicity or disease processes. Specific research goals include (1) improve methods for monitoring for the presence of pathogens, toxins and contaminants in seafood products, (2) characterize the environmental and climate conditions that may be favorable for potential biotoxin and pathogen outbreaks, (3) develop technologies to remove chemical contaminants from fish feed and to enhance the nutritional content of aquaculture products, (4) develop a better understanding of the net economic and health benefits of seafood consumption balanced with the risk of exposure to pathogens, toxins and contaminants, and (5) develop new mechanistic animal models for the study of infectious diseases, as well as toxicological, physiological, and biochemical processes relevant to marine animal and human health.
Support collaborative community-based data collection, dissemination, and analysis for fishers, fisheries management, science, marketing, seafood safety, and education
Data are no longer the sole province of the agency. As technologies advance, fishers are collecting and analyzing fleet data in near real time. Data collected by fishers are used by the fishing community to reduce bycatch, allocate fishery impacts, and trace products through the processing and marketing system. Fisher-collected data, in combination with survey and oceanographic data, satellite remote sensing, economic data, and sociocultural data provide improved understanding of fish stocks, fishing, and the near-shore ecosystem. Collaborative efforts increase the quantity and quality of data available to the agency for scientific analysis, modeling, fishery management, and conservation. Through cooperation with the science and management agencies, the fishing community stands to gain more control and flexibility of their fishing operations, including the potential for improved economic efficiency. Increased availability of fisheries data creates opportunities for education and outreach both in the school system and to the general public. Further, well-informed local leaders conversant in the latest fishery issues will help garner local support and fisher buy-in for improved information sharing. The NWFSC will work with industry groups to improve distributed data collection, compilation, and distribution for multiple uses in fisheries, management, science, marketing, and education.


genus of pathogens of interest
the quantity or amount of something
climate change
changes in climate


Vibrio population structure


Phylum Proteobacteria


Mark Strom
Principal Investigator
Rohinee Paranjpye