The latest big recall involves peanut butter believed tainted with salmonella, a bacterium found in feces that can cause severe diarrhea. The outbreak has sickened at least 329 people in 41 states since August, federal health officials say.

Food safety experts say it would be impossible to know whether increased numbers of inspectors and inspections would have prevented the outbreak, linked to Peter Pan and Great Value brands made by ConAgra Foods Inc., or other recent food poisoning scares.

The FDA had last inspected ConAgra's peanut butter plant in Sylvester, Ga., in February 2005 and had found no problems, agency spokesman Michael Herndon said.

Firms that produce high-risk foods more susceptible to contamination, such as fresh fruit and vegetables, are supposed to be inspected every year, unless they have a good safety record. Then inspections are done every two or three years, Herndon said.

For other foods, the FDA rotates inspections, depending on resources.

FDA food inspectors look for filth, decomposition, adulteration with pesticides and industrial chemicals and the illegal use of color or food additives, according to the agency.

Inspectors also look for sources of possible contamination, such as flies. For instance, inspectors are asked to count flies, as well as how often they land on a food product. They're also told to look for any open doors or damaged window screens that could allow the insects to flit back and forth between the product and, say, a toilet, floor drain or garbage can, according to agency documents.

The shrunken ranks of inspectors have left the nation once again vulnerable, especially to problems in imported food, Thompson and others said. Doyle, whose center studies ways to improve food safety, called the nation's growing appetite for imported foods the "coming threat."

The United States last year imported about $10 billion more in food, feed and beverages than it exported, according to Census figures. Even as imports grow in volume and diversity, the number of FDA inspections is shrinking: agency inspectors physically examined just 1.3 percent of food imports last year, about three-quarters as much as in 2003.

The FDA, meanwhile, says it is concentrating its efforts on areas where the potential threat to the public's health is greatest.

"We're applying resources to targeted areas. So in a way, it's not a matter of 'Are you inspecting one out of 100 or 10 out of 100?' The real issue is if you can define risk. Are you applying the 10 inspectors to the 10 areas of concern? Then it's essentially you're covering 100 percent of your problem, which is not covering 100 percent of the universe," FDA commissioner Dr. Andrew von Eschenbach said.