ATLANTIC CITY - Researchers say they have found strains of bacteria in Delaware Bay shellfish that could pose a health threat to people with weakened immune systems.

Gary Richards is the lead scientist for the U.S. Agriculture Department's seafood safety laboratory in Dover, Del., and the lead author of the two-year study, published in this month's edition of Applied and Environmental Microbiology.

He called the study results a "wake-up call to monitor the shore more closely."

Researchers caution that those in danger of getting sick should not be eating raw shellfish anyway.

Still, researchers found two potentially dangerous species of the bacteria

shewanella

and one species of

photobacterium

in oysters and seawater in the bay.

The study, coauthored by Iris G. Burt and David Bushek of Rutgers University's Haskin Shellfish Research Laboratory in Port Norris, N.J., says the bacteria could cause skin and blood infections.

Oyster companies in the bay already voluntarily shut down harvests the last two weeks of June, when bacteria can flourish.