CHICAGO, IL — Bacteria that cause food poisonings aren’t going away, despite the efforts of the food industry to eliminate them, according to a report from the Institute of Food Technologists.

New germs arrive in imported foods and bacteria already here develop in new forms, the IFT report indicates. In fact, the bacteria Listeria monocytogenes are so common in the environment, it’s “practically impossible” to keep food entirely free of them.

“Zero risk is not a reality,” the report says.

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 by coming into contact with crops.

Manure, which harbors bacteria such as E. coli O157:H7, campylobacter 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 also warns against overuse of antibiotics in livestock, saying there is growing evidence that it’s causing bacteria to become resistant to drugs.

“The job of assuring microbiological food safety is unending,” says Morris Potter, a top U.S. Food and Drug Administration epidemiologist who chaired the study by government and university scientists.

Consumers “should take heart, however, because of the progress that has been made.”