Spray Guards Chicks from Infections

by J. Raloff

A drug spray that wards off Salmonella infection in newly hatched chickens has just been approved by the Food and Drug Administration. Preliminary tests indicate that the drug, Preempt, also thwarts infection by Campylobacter, Listeria, and the deadly Escherichia coli O157:H7, thus holding out the prospect of greatly reducing food poisoning caused by poultry.

Designed to be sprayed on hatchlings, Preempt consists of 29 types of living, nontoxic bacteria isolated from the gut of mature chickens. As it preens, a treated chick ingests the bacteria, seeding its ceca -- intestinal cul de sacs -- with the beneficial microbes. The bacteria cover niches in the cecal surface so quickly and heavily that intestinal pathogens find it all but impossible to move in, explains Donald Corrier, a veterinary pathologist with the U.S. Department of Agriculture in College Station, Texas, and a developer of the drug.

Because the ceca are where Salmonella reside, Corrier notes, "if you can keep them out of there, they're out of the bird." Indeed, his tests indicate that a single treatment can confer lifelong protection on 99 percent of chickens.

"The unique thing about our culture [of bacteria]," Corrier told Science News -- and the key to its approval -- "is that we know exactly what bugs are in it." While the precise function of each member is not known, he says, the microbial combo provides "an ecosystem that is very similar, on a small scale, to what's in an adult chicken."

While the spray may reduce the number of infections in chickens, "I'm concerned about whether consumers will think that because birds have been 'Preempted,' they might not have to take all the normal precautions when preparing chicken at home," says Amy L. Waldroup, a poultry scientist at the University of Arkansas in Fayetteville.

Corrier agrees that since even treated birds may become contaminated during food processing or in the kitchen, cooks must continue to practice good hygiene when working with eggs or raw chicken. However, adds John R. DeLoach, a former coworker and a Preempt developer, use of the drug may someday make the concentrations of the pathogens "so low that they aren't important."

Last week, orders to purchase Preempt began flooding MS Bioscience of Dundee, Ill., which is licensed to market the drug. By Friday, notes DeLoach, the company's vice president, "I had more orders than I can fulfill in the next 10 months." The customers include "large poultry integrators," he said, "who want to try our product on their entire complex -- millions of chickens." In Japan, where the drug has been available for more than a year, customers are equally divided between those who raise chickens for meat and for eggs.

Indeed, for coping with Salmonella in chickens and eggs, "this [drug] looks like the best available option," notes Donald J. McNamara, executive director of the Egg Nutrition Center in Washington, D.C.

Poultry doesn't provide the only market for bacterial treatments, Corrier observes. His group is trying out a swine-tailored mix on newborn pigs, and a third assortment is under development for calves.

"Ultimately, this is going into humans," DeLoach predicts. It may take 5 to 7 years to clear the FDA hurdles, he says, "but there's no question that we can come up with a [mix] for humans that can be used to alleviate all sorts of intestinal imbalances," such as those that can occur when therapeutic antibiotics wipe out many of the good bacteria in the gut.   

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