With food safety issues becoming more common, consumers are putting pressure on the livestock industry to come up with some alternative answers. One such area of focus is microbial antibiotic resistance.

Researchers at Iowa State University are trying to take a long-term approach to this issue by showing that antibiotic alternatives administered shortly before a hog is slaughtered can reduce Salmonella risks associated with the carcass. “The timing is important because many scientists believe the risk for contamination increases during the periods when pigs are transported and held at the packing plant,” says Hank Harris, Iowa State microbiologist, who is heading the project.

Although the ultimate goal is to work with Salmonella levels in market hogs, Harris began his studies using Isowean pigs. The newly weaned pigs are easy to work with and cost less than market hogs.

Each year, foodborne Salmonella makes between 2 million and 4 million people sick. “If resistant Salmonella makes its way to humans via foods, it could pass on its resistance to other organisms, making it harder to treat other human diseases,” says Harris.

Harris explains that he started working on finding alternatives to antimicrobials in 1998 when the National Pork Producers Council put out a special request for such research. Prior to that, he notes, it was hard to obtain funding strictly for food safety research projects.

At first, producers and some industry leaders were concerned that it would raise a red flag for pork if the public learned how many swine herds were already infected with Salmonella. “The scientific community accepts the theory that any Salmonella found in pigs is considered to cause diseases in humans,” contends Harris.

Plus, market competition has upped the ante. Danish producers are experts at marketing pork, as well as using technology to detect Salmonella and consequently have less of it in their pigs at slaughter. This has given them a strong sales tool, especially in export markets.

“We thought if we could bring in technology from Denmark on how to detect Salmonella on the farm it would be accepted, but it wasn’t,” he says.

One reason it wasn’t is because the Danish system, which involves a test to determine which herds are shedding high levels of Salmonella at slaughter, would be hard to implement in the United States. In Denmark, pork producers own their slaughter plants giving them control over how their pigs are marketed. If a producer’s herd has a Salmonella problem, he or she is penalized. Right now, Harris says U.S. packers aren’t paying premiums or penalizing producers for implementing food safety technologies. He notes that some of the integrators are in the best position to implement the Danish system.

Here’s where Harris and his research team step in. Harris’ project is researching two alternatives. The first involves probiotics, which encourage the growth of “friendly” bacteria to prevent disease-causing bacteria from getting out of control. In preliminary studies, Salmonella declined in the weaned pigs fed milk containing Lactobacillus, a bacterium taken from the pigs’ intestinal tracts.

Essentially, Harris is feeding a yogurt-like liquid mixture to weaned pigs once a day. The pigs were newly weaned – two to three weeks old – when the trial began, and it lasted five to six weeks. “Lactobacillus is a common yogurt culture,” he explains

The other alternative involves bacteriophages, which are viruses that infect and kill bacteria. Once again, early results show that weaned pigs given bacteriophages either orally or by injection have less Salmonella than other pigs. If future studies show positive results, Harris says producers could administer bacteriophages to market hogs hours before slaughter to reduce Salmonella and other bacteria.

Working with Harris is Isabel Harris, epidemiologist; and graduate students Chris Baum, probiotic study, and Nakhyuang Lee, bacteriophages study.

“The preliminary data tells us that both options reduce Salmonella, in weaned pigs,” says Harris. “We want to repeat the tests using older, market-ready pigs. If the results are positive, producers could decrease Salmonella levels in their pigs by using the method two or three weeks before slaughter.”

“It’s important to remember that we don’t prevent disease with these (probiotics and bacteriophages),” explains Harris. “We are trying to find out if we can reduce the level of human disease-causing organisms in pigs. This is a much more difficult problem than simply preventing a pig disease from occurring.”

If these antibiotic alternatives show promise, the next step is for Iowa State researchers to train producers, veterinarians and processors to implement them. To comply with the grant, training must take place within two years.

As an added note, Harris says there are commercial feed additives that contain Lactobacillus, but none have been evaluated in terms of reducing Salmonella. Therefore, researchers will have to determine whether the yogurt-like mixture, any existing products or a combination of both will work. Harris admits that feeding the liquid yogurt-like mixture is rather labor intensive.

The current projects are possible thanks to a USDA $600,000-integrated-food-safety grant and other funds from the Biotechnology Research Development Corporation,National Pork Producers Council, PICand Food Safety Consortium at Iowa State.

To compliment the current research, Harris and co-investigators from Iowa State, Isabel Harris, Joan Cunnick and Mike Daniels, submitted a $1-million proposal for a study to the USDA national research initiative to determine if drug-resistant Salmonella on the farm is showing up in pig carcasses. The researchers expect to have an answer by May or June.

Like it or not, U.S. consumers are becoming more wary of antibiotic use in pork production, and drawing their own conclusions. Consumers in Europe and other countries are already wary. To curb the fears, the U.S. pork industry has to take a pro-active approach. Harris contends, “the pork industry needs to determine if the use of antimicrobials in pork production contributes to antibiotic resistance in human foodborne pathogens. Currently, no one has a concrete answer, but there is a lot of speculation. We have the molecular genetic tools to determine the answer, and will likely know in three to five years.”

Finally, no matter what the outcome, consumers are demanding stepped-up food safety attention now. “We may need to find alternatives to antibiotics for pigs whether we like it or not,” he notes. “You can’t pick up a newspaper these days without reading something about food safety. It’s in our best interest to find some answers.”

For more information about his research, you can contact him at (515) 294-1664 or hharris@iastate.edu.