USDA Announces New E. coli O157:H7 Vaccines
The USDA's Agricultural Research Service (“ARS”) has announced that its scientists have developed two vaccines that might reduce the spread of E. coli O157:H7 in cattle.
"Preventing E. coli O157:H7 from proliferating inside cattle helps limit contamination of meat at the packinghouse, and reduces shedding of the microbe," ARS said in a statement. "Manure-borne E. coli can sometimes be moved by rainfall into drinking water. What's more, in some instances, it can end up in irrigation water, and can potentially contaminate fruits, vegetables and other crops, increasing risk of an outbreak of food-borne illness."
The first form of the vaccine is comprised of cells of a strain of E. coli O157:H7 that lacks a gene called hha. A second form of the vaccine contains an E. coli strain that lacks both hha and a second gene, sepB. In each of the vaccines the E. coli strain produces immunogenic proteins, which trigger an immune system response that prevents E. coli O157:H7 from successfully colonizing in cattle intestines.
In preliminary tests, 3-month-old Holstein calves were immunized with a placebo or either form of the vaccine. Six weeks later, the animals received a dose of E. coli O157:H7 and for the next 18 days, their manure was tested for evidence of the microbe. Calves that received either vaccine had reduced or non-detectable levels of E. coli within only a few days after being inoculated with the bacteria.
Research microbiologists Vijay K. Sharma and Thomas A. Casey developed the vaccines in their laboratories at the agency's National Animal Disease Center in Ames, Iowa.
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