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John Ewart (left), an aquaculture/fisheries specialist (University of Delaware), and ARS microbiologist Gary Richards examine freshly harvested oysters on board the Center for the Inland Bays' work boat before transport to the laboratory. Click the image for more information about it.

Research Reveals Functions of Harmful Shellfish Pathogens

By Jim Core
March 4, 2005

Providing safer shellfish is the goal of Agricultural Research Service (ARS) scientists who are studying the means by which pathogenic bacteria enter shellfish.

In the United States, two pathogenic bacteria from the genus Vibrio are of concern: V. vulnificus and V. parahaemolyticus. These bacteria are naturally found in shellfish and seawater, particularly when water temperatures are warm, and can lead to serious health concerns.

ARS scientists at the Microbial Safety of Aquaculture Products Center of Excellence in Dover, Del., are studying these bacteria with the goal of keeping them out of shellfish. Gary P. Richards, a microbiologist and the center's lead scientist, wants to identify Vibrio enzymes that may help the organism enter shellfish--and, eventually, a human host.

Richards, who leads a group of scientists from Delaware State University and the National Institutes of Health, recently discovered in V. vulnificus an enzyme called phosphoglucose isomerase. This enzyme could provide a way for Vibrio to spread more easily.

He also detected the enzyme in virtually all species of Vibrio tested, but not in non-Vibrio pathogens. The enzyme is capable of producing what are called vasoactive peptides, which could contribute to rapid spread of V. vulnificus in humans. A study of V. vulnificus in oysters suggests that strains virulent to humans may be more invasive to--and persistent in--oysters.

The Dover center, a field location of the ARS Eastern Regional Research Center in Wyndmoor, Pa., also studies methods to detect norovirus and the hepatitis A virus in shellfish. It also develops high-pressure processing techniques to inactivate enteric viruses in contaminated shellfish.

This research may provide better diagnostic capabilities and treatment strategies to further reduce shellfish-related illnesses.

Read more about this research in the March issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.