A new electrostatic air cleaning system reduced airborne salmonella by 94 percent in a commercial hatchery in Georgia in a recent ARS study. Hatching cabinets are a primary source of salmonella contamination for broiler chickens. A single infected chick can spread salmonella to all of the chicks in a hatching cabinet. The new system captures dust that harbors hitchhiking organisms such as salmonella. Dust is electrostatically charged and captured on special plates that are automatically washed at prescribed intervals. Results of the most recent commercial experiments showed a 77 percent reduction in dust levels on average and 94 percent less enterobacteriaceae (commonly encountered bacteria such as salmonella or E. coli that frequently cause disease) than a cabinet treated with hydrogen peroxide disinfectant. The system has also been shown to reduce airborne Salmonella enteritidis in a caged layer room by 95 percent and to have a strong killing effect on salmonella at close range.

Southeast Poultry Laboratory, Athens, GA
Bailey Mitchell, (706) 546–3443, bmitchell@seprl.usda.gov

A jellyfish gene is helping researchers discover how a food-poisoning bacterium, Escherichia coli O157:H7, can colonize fresh lettuce. An ARS scientist has inserted a gene from the Aequorea victoria jellyfish into laboratory strains of this foodborne pathogen. The gene cues production of a bright-green, fluorescent protein. When leaves of romaine, green leaf, and iceberg lettuces are artificially infected with the genetically engineered E. coli for laboratory investigations of the pathogen, the fluorescence acts as a readily detectable marker, making it faster and easier to spy on the microbe. The fluorescence-based assay should help food safety scientists test the effectiveness of new tactics designed to keep E. coli out of food. Though outbreaks of E. coli O157:H7 linked to contaminated lettuce are infrequent, researchers want to help growers, processors, and consumers ensure that the popular leafy vegetable remains safe to eat. Earlier, other researchers moved the fluorescence gene into other organisms. But the ARS team is among the first to employ fluorescing E. coli O157:H7 to track this microbe's movements in plant tissue. E. coli O157:H7 can cause bloody diarrhea and in some instances can lead to acute kidney failure, requiring patients to undergo dialysis. The microbe is unusual in that most other bacteria in the same family are harmless to humans.

Food Safety and Health Research Unit, Albany, CA
Marian R. Wachtel, (510) 559–5957, wachtel@pw.usda.gov