Beneficial strains of fungi are the star players in a new antiaflatoxin program planned for spring of 1999 on 20,000 acres of Arizona cotton. Certain strains of Aspergillus flavus fungi and related fungi produce aflatoxin, a potential carcinogen. In Arizona, aflatoxin contamination costs cotton growers an estimated $3 million to $8 million each year. The campaign against it depends on ARS-developed technology. Under an experimental use permit from the U.S. Environmental Protection Agency, farmers will apply beneficial fungi as a biopesticide. Developed by ARS scientists, these fungi are atoxigenic—nonaflatoxin producing—strains of A. flavus. When applied to the soil beneath cotton plants, the good-guy strains crowd out or exclude the bad-guy Aspergillus from choice nutrients and space. This undermines the bad fungi's ability to spread to the crop and produce aflatoxin. Federal law prohibits cottonseed with more than 20 parts per billion of aflatoxin from being fed to dairy cattle. Until recently, cotton farmers could do little to reduce contamination, other than harvest crops early and control insects that spread the fungi. ARS has tested the new approach, called "competitive exclusion," on more than 1,100 acres of cotton since 1996. The tests show that the approach reduces contamination by 90 percent. To expedite Arizona's program, ARS scientists supplied EPA with 1,200 pages of scientific data on the safety and efficacy of the atoxigenic fungi.
Southern Regional Research Center, New Orleans, LA
Peter J. Cotty, (504) 286-4391, pjcotty@commserver.srrc.usda

New high-tech tests more quickly detect a key organism that can cause food poisoning. ARS researchers developed the tests to detect Shiga-toxin-producing E. coli (STEC) strains, such as E. coli O157:H7 in cattle feces and beef. These bacteria form toxins and other proteins that contribute to diarrhea in infected animals. The new test uses a technique called fluorescent PCR (polymerase chain reaction). In this process, scientists first amplify the organism's DNA using PCR. Then they use a fluorescent detector to illuminate the DNA. Results from the test can be obtained within 4 hours, which is 4 to 8 hours faster than other laboratory procedures. The researchers tested more than 60 strains, demonstrating 100 percent accuracy in detecting STEC and distinguishing E. coli O157:H7 from other STEC strains. These tests will be useful to cattle producers and veterinarians for fast diagnosis of diarrhea caused by STEC bacteria in calves. Cattle producers need this information to meet federal restrictions against the presence of E. coli O157:H7 on animal carcasses. The bacteria are transmitted to humans who eat foods contaminated with infected animal feces. About 20,000 human cases of E. coli O157:H7 infection are reported annually in the U.S., according to the Centers for Disease Control and Prevention.
National Animal Disease Center, Ames, IA
Vijay Sharma, (515) 239-8279, vsharma@nadc.ars.usda.gov

A simple three-step process can help poultry producers keep Salmonella and other food pathogens out of poultry—and may increase profits, according to an ARS trial in cooperation with a Georgia poultry producer. Each step blocks contamination at a critical point in the bird's life cycle. Farmers would spray freshly laid eggs with a mild detergent and a reliable farm disinfectant chemical; hatcheries would spray a fine mist of hydrogen peroxide in the cabinet while chicks are hatching; and young chicks would receive benign gut bacteria from healthy mature chickens to prevent Salmonella colonization in the grow-out house. Working with a farmer, an ARS researcher confirmed the effectiveness of the first step. This producer found cleaning and disinfecting eggs paid for itself because more eggs were sold at a higher price. Estimates are that a large-scale farm selling millions of eggs annually could recover the cost of the spraying equipment in 2 years.
Richard B. Russell Agricultural Research Center, Athens, GA
Mark Berrang, (706) 546-3551, mberrang@ars.usda.gov.