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Will Oil-Eating Bacteria Plague the Gulf?

By Dan Flynn and Suzanna Schreck

As though the Gulf Coast states don't have enough to worry about with crude oil spewing into the water at an estimated rate of 5,000 barrels a day, they soon may also have to worry about bacterial plumes.
A microbe called Vibrio parahaemolyticus, common in warm coastal waters like the Gulf, thrives off of crude oil.  "You can feed it exclusively oil," Jay Grimes, a marine microbiologist at the University of Southern Mississippi, said of the Vibrio species.
When ingested by humans, usually from eating raw oysters, Vibrio and related organisms can cause cramps, nausea, and can sometimes be fatal.  More than 4,500 people are infected with the bacteria each year.
Though harmful to humans, these single-cell organisms aid in keeping the ocean healthy by eating naturally seeping oil.  Without their presence, the world's oceans would be covered in a thick film of oil.
The organisms surge in response to hydrocarbons, molecules made up of bonded hydrogen and carbon, which are naturally found in oil.  
Scientists in the Gulf are unsure if these bacteria are already surging in the oil spill area.  It is also unknown whether or not the bacteria will continue to grow once the oil's hard remnants settle into the sediment on the ocean floor.
Another relative of the Vibrio species is vulnificus, which when ingested, kills dozens of Americans each year.  Raw oysters are the primary carrier of the bacterium, which has caused heated safety debates between health officials and Gulf politicians.
Some scientists speculate that the combination of summer heat and the oil spill could raise the chances that Vibrio bacteria could grow in larger than usual numbers.  
"The question is: Will there be an inadvertent enhancement of the growth of these potential human pathogens?" Former director of the National Science Foundation and marine microbial life expert Rita Colwell told a reporter.  "It's a question, and the answer is uncertain," she said.
According to Jim Oliver, Vibrio specialist at the University of North Carolina, Charlotte, "There's no question bacteria, in general, increase following spills, and this includes Vibrios..."  Oliver continued to explain that with Vibrios, "significant increase is unsure, I would say, but they are coastal bacteria... so [they] could well increase either as a direct result of oil degradation or as a side effect of the added nutrient levels."
Oliver confirmed that the combination of oil, the presence of live and dead bacteria, and the summer heat is worrisome.  "I think that combination could lead to very serious public health concerns," he said.
Spokeswoman Meghan Scott for the Food and Drug Administration (FDA) said the organization is aware of the Vibrio threat in the Gulf.  
"Closure of oyster harvesting areas is based upon the presence of oil, and reopening cannot occur until the presence of oil is gone and shellfish have been tested by sensory and chemical analysis," Scott said. "Concurrent with acceptable test results for oil in oysters, Vibrio levels will have returned to background."
Vibrio controls established by the FDA will be enforced by local shellfish control authorities at the time of harvest.  
At the present time, oil continues to flow into the area which has crippled the local fishing industry.  It is still unknown how officials will stop the oil spill and when areas of the Gulf will re-open for fishing.

Image:  This scanning electron micrograph (SEM) depicts a grouping of Vibrio vulnificus bacteria; Mag. 13184x. 

Vibrio vulnificus is a bacterium in the same family as those that cause cholera. It normally lives in warm seawater and is part of a group of vibrios that are called "halophilic" because they require salt. V. vulnificus can cause disease in those who eat contaminated seafood or have an open wound that is exposed to contaminated seawater. Among healthy people, ingestion of V. vulnificus can cause vomiting, diarrhea, and abdominal pain. In immunocompromised persons, particularly those with chronic liver disease, V. vulnificus can infect the bloodstream, causing a severe and life-threatening illness characterized by fever and chills, decreased blood pressure (septic shock), and blistering skin lesions. V. vulnificus bloodstream infections are fatal about 50 percent of the time.

CDC/Colorized by James Gathany. 

Full post as published by Food Safety News on July 01, 2010 (boomark / email).