In a report for the Institute of Food Technologists, the scientists also say the increasing use of manure as fertilizer poses the risk of spreading harmful bacteria to food, either by contaminating irrigation water or coming into direct contact with crops.
which harbors bacteria such as E. coli O157:H7 and salmonella, substitutes for chemical fertilizer on both organic and conventional crops. In some foreign countries, chicken manure is fed to farm-raised shrimp.
The report, released Wednesday, also warns against the overuse of antibiotics in livestock, saying there is "growing body of evidence" that farm use of antibiotics is causing bacteria to become resistant to drugs.
"The job of assuring microbiological food safety is unending," said Morris Potter, a top epidemiologist for the Food and Drug Administration who chaired the study by government and university scientists. Consumers "should take heart, however, because of the progress that has been made."
The scientists say it will be "practically impossible" to keep hot dogs and similar precooked meats free of Listeria monocytongenes because the bacterium is so common in the environment.
The report does not address the issue of whether the government's food safety agencies should be consolidated. Food regulation is now split between the Agriculture Department and FDA, which have widely varying inspection programs and rules.
But the report raises concern about the regulation of imported fruits and vegetables and the potential for new pathogens getting into the country. It's happened before: The bacteria, Cyclospora cayetanensis, came to the United States through imported
produce, and rare forms of salmonella also have been appearing in the country.
"Certainly, you can grow produce that is free of pathogens in developing countries. It's just a matter of sanitary practices and the quality of water that is used for irrigation," said Michael Doyle, a University of Georgia microbiologist who assisted in the study.
FDA inspects less than 2 percent of imported fruits and vegetables. Major supermarket chains, worried about new outbreaks of salmonella and other bacteria, have recently started requiring domestic and foreign produce suppliers to be inspected by private firms.
The report says better monitoring of foodborne illnesses is needed to spot trends and identify causes. For example, doctors too often treat patients for food poisonings without reporting the illnesses to public health authorities or ordering tests to determine the exact causes.
That lack of reporting means that government agencies and food companies may not be aware of new pathogens or dangerous products.
Changes in how foods are processed - such as leaving out salt or replacing fats with gums - can lead inadvetently to new safety problems by making food more hospitable to bacteria, or by causing the bacteria to evolve into hardier forms.
At one point, yogurt manufacturers started replacing sugar with an artificial sweetener only to discover
that led to the growth of the bacteria that causes botulism. It turned out that the sugar was removing water from the yogurt, making it difficult for the bacteria to grow. Yogurt was reformulated to eliminate the problem.
Food makers also must be careful that their attempts to inhibit bacteria growth don't backfire. For example, an antimicrobial ingredient or treatment that doesn't kill the bacteria may cause bugs to develop into stronger forms.
"There are a lot of complicated factors that result in foodborne illness," said Jenny Scott, senior director of food safety programs for the National Food Processors Association. "You can focus in on one aspect, but things change. You think you are licking them, but something else pops up."
By Philip Brasher© MMII The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed