The USDA plans to start testing for Salmonella bacteria in plants that process turkeys. The department for years has been doing similar carcass testing in plants that slaughter hogs, cattle and chickens.

During Agriculture Department testing of turkeys in 2001 and 2002, about 13percent of the samples turned up positive, a comparable rate to chickens but much higher than in hogs or cattle. Contamination rates have been found to vary widely among turkey processors. Agriculture Department test results in 2001 found rates varying from zero to 49percent.

The testing in turkey plants is due to start in May or June as is part of a broader plan to reduce the number of Salmonella infections, which have been rising even as illnesses from other types of food-borne germs, such as E. coli, Campylobacter and Listeria, have been declining.

The department said it will consider further measures after reviewing test results during a 12-month period expected to start in July. One idea the agency said it favors is publicly releasing the test results of some plants.

Industry officials say producers and processors have been working to reduce Salmonella contamination through better sanitation practices on farms and the use of chlorine and chemical rinses to clean turkey carcasses. The National Turkey Federation has commissioned a study to evaluate various procedures to determine their effectiveness.

On farms, producers can avoid contaminating birds by making sure that boots and equipment are clean before entering the turkey houses, and by proper handling of water lines, feeders and litter.