Sustainable solutions to boost chicken gut health to reduce salmonella

Researchers at Iowa State are developing a probiotic with several key beneficial microbes
calendar icon 2 July 2024
clock icon 10 minute read

At Iowa State University, scientists are working to boost chicken gut health to help reduce salmonella infections in poultry and people. Others are honing faster, affordable methods for detecting foodborne pathogens and harnessing algae to treat wastewater.

Their work highlights some of the ways Iowa State is developing patented technologies to make food safer and water cleaner.

Improving chicken gut health

We are surrounded by and steeped in microbes. Trillions live on our skin and in our bodies, helping us digest food and absorb nutrients, fight infections and even manage stress. We rely on them to fix nitrogen for plants and decompose waste and use them to make sourdough bread and yogurt.

But of course, some microbes cause us harm.

Around 48 million people in the US get sick each year from foodborne pathogens, according to the US Centers for Disease Control and Prevention. The CDC estimates one of the top culprits, salmonella (non-typhoidal) bacteria, cause 26,500 hospitalizations and 420 deaths, annually. According to the US Department of Agriculture, nearly a quarter of the 1.3 million human infections each year are attributed to poultry.

Melha Mellata is an associate professor of molecular microbiology at Iowa State and chair of the interdepartmental microbiology graduate program. Her research includes the development of new treatments and procedures to mitigate bacterial infections in food producing animals and humans.

“Salmonella bacteria live in the guts of many animals, but in some hosts, like chickens, salmonella tricks the animal’s gut into thinking it’s not bad. Since there’s no immune response, the animals carry the bacteria without showing symptoms,” says Mellata.

Without symptoms, Mellata says it’s much harder for farmers and processors to know if poultry are infected. They try to reduce the risk of salmonella by sanitizing equipment, running meat through chemical washes and testing products before they go to consumers, which is required under federal law.

Yet, bacteria can still slip through the supply chain and end up in restaurants and home kitchens.

Mellata emphasizes the US has one of the safest food supplies in the world. But with certain salmonella strains becoming resistant to antibiotics and even detergents, it’s getting harder and more expensive to prevent infections. That’s a big deal for Iowa, the top egg-producing state.

“If we can reduce salmonella from the source, we will have healthier, more productive animals and spend less money trying to remove pathogens from the food at the end of the supply chain,” says Mellata.

The researcher and her Ph.D. students aim to do this by developing a probiotic with several key, beneficial microbes. One they identified is segmented filamentous bacteria. Traditionally, SFB is transferred from hens to chicks shortly after they hatch, says Mellata. But in most commercial poultry operations today, chicks hatch in incubators, away from their mothers.

Ph.D. student Jared Meinin-Jochum performs isolation trials with SFB using a pipette inside a low oxygen chamber in Melha Mellata’s Food Sciences Building lab. Photo by Christopher Gannon/Iowa State University.
Ph.D. student Jared Meinin-Jochum performs isolation trials with SFB using a pipette inside a low oxygen chamber in Melha Mellata’s Food Sciences Building lab

The researchers found chicks that were inoculated with SFB shortly after hatching were able to fight salmonella infections much better later on compared to those that were not inoculated. Specifically, SFB in the gut microbiota triggered the production of T-cells and antimicrobials that attack salmonella.

With a pending patent through ISU Research Foundation, the researchers want to turn their discovery into a commercial probiotic. They envision a powder that can be sprinkled onto food or mixed with water for chicks within the first 24 hours of hatching. Mellata says this would be an easy and inexpensive solution for producers.

Her team is continuing to search for more key microbes that could improve the health of chickens and keep pathogens, like salmonella, in check.

“Let's help chickens build their gut immunity so they can fight infection on their own,” says Mellata.

Detecting foodborne pathogens

While Mellata’s lab works on prevention at the farm, another team is trying to help catch pathogens before food is shipped to consumers.

Byron Brehm-Stecher, an ISU associate professor of food microbiology, says foodborne outbreaks have been around since the “dawn of agriculture.” But thousands of years ago, they were usually limited to a small group of people in one location.

“In order to feed our growing world population, we have become very efficient in our abilities to produce, package and distribute foods, quickly and globally,” says Brehm-Stecher.

He explains the downside to this efficiency is that a single point of contamination can spread much further to more people. An estimated 224,000 people in the US had food poisoning after eating a popular brand of ice cream in 1994. It was one of the largest outbreaks in US history. After a multi-year investigation, health officials traced salmonella to tanks that were used to haul raw eggs and an ice cream mix, without proper cleaning and sanitation between loads. The food company made several changes to prevent future outbreaks, including another pasteurization step and more testing.

“We need checkpoints at different levels to reduce the possibility that something will get in there. Developing detection methods that are affordable and easier to use are part of a multi-tier strategy to keep our food safe,” says Brehm-Stecher.

Several years ago, Brehm-Stecher teamed up with Jared Anderson, the Alice Hudson Professor of Chemistry at Iowa State, to work on a faster, affordable detection method with magnetic ionic liquids (MILs).

Ph.D. student Shashini De Silva holds a vial with a liquid solution containing E. coli bacteria and a small amount of cobalt MIL. Photo by Christopher Gannon/Iowa State University.
In Anderson’s lab, Ph.D. student Shashini De Silva holds a vial with a liquid solution containing E. coli bacteria and a small amount of cobalt MIL. Like olive oil, the MIL is hydrophobic; it doesn’t mix completely with the water in the sample

Anderson credits a graduate student in his lab with discovering that MILs could capture bacteria in water. The outer surfaces of microbes generally have negative charges, which can stick to the positively charged MIL.

From there, the researchers started experimenting with milk and a liquid egg product.

“Microbes may be present at very low levels in the container of food or distributed unevenly, like needles in a haystack. So, we may need to grow them in a liquid broth or use a DNA amplification reaction to get the cells or their DNA to a level where we can detect a pathogen, if present,” says Brehm-Stecher.

With the “enrichment” method, the researchers create an environment that’s favorable for some microbes to grow and unfavorable for others. Salmonella colonies popping up on a cell plate or in the broth confirms that the original food product was contaminated.

Another method, isothermal DNA amplification, uses enzymes in a test tube to make enough copies of a pathogen’s genetic material to allow detection.

Anderson says enrichment cultures are still “the gold standard” for food manufacturers, but it’s not the best at providing quick results. The process usually takes a minimum of 24 hours if done in house and longer if samples are shipped to a lab.

By pairing the MIL method with isothermal DNA amplification, the researchers say food manufacturers can get results in as few as 10 minutes. This process is also more affordable and portable compared to other alternatives. The MILs could be reused, and in situations without electricity or other resources, the isothermal process can function with commercial hand warmers.

Anderson and Brehm-Stecher say several companies have expressed interest in licensing the patent through ISURF. In the meantime, they’re continuing to experiment and fine-tune the chemical structure of MILs. One of their long-term goals is to create a modified MIL that can target specific pathogens, like salmonella.

“Something I find very exciting at land-grant universities is being able to come up with cool ideas and then translate them into things that can make an impact on the world,” says Brehm-Stecher.

Both Brehm-Stecher and Anderson emphasize graduate students have been instrumental to their research, and they value the opportunity to collaborate with faculty in other departments and universities. They recently started working with colleagues at the University of Massachusetts Amherst on concentrating and capturing viruses from food with MILs. They say the data collected so far show promising results.

Harnessing algae to clean water

Across the US, wastewater treatment plants are looking for cost-efficient solutions to meet new state and federal water quality requirements. This includes lower thresholds for the amount of nitrogen and phosphorous that can be discharged into rivers and lakes.

All organisms need nitrogen and phosphorous to grow. But high concentrations of these nutrients in waterbodies can cause certain types of algae to grow faster than normal. “Harmful algal blooms” create dead zones and some species of algae also release toxins that can sicken or kill wildlife, pets and people.

Algal blooms pose serious environmental and public health risks and threaten economies dependent on fishing and tourism. Ironically, algae can also be part of the solution.

“‘Algae’ includes a large and very diverse group of organisms, somewhere between 5,000 and 10,000 species that range from single-cell diatoms to giant kelp,” says Zhiyou Wen, director of Iowa State’s Center for Crops Utilization Research. He’s also a professor in the department of food science and human nutrition.

Over the last two decades, Wen has investigated the use of certain species of algae as food ingredients, and more recently, as an “effective, reliable, and economical” way to treat wastewater.

The researcher and one of his former students, Martin Gross, developed a novel system called Revolving Algal Biofilm (RAB) to grow algae and remove nitrogen and phosphorous. After a successful pilot project at Iowa State’s BioCentury Research Farm, they co-founded Gross-Wen Technologies in 2014. They attracted state and federal grants and investors, and licensed the patented revolving algal biofilm system through ISURF.

With the RAB system, algae grow on a series of large, vertical conveyor belts that rotate in and out of a wastewater reservoir. “Like skyscrapers, you can fit a lot more into a space by going up rather than out,” says Wen.

The microorganisms absorb nitrogen and phosphorus from the wastewater, and sunlight and carbon dioxide from the air. A greenhouse encloses the RAB system, which Wen says is more cost-efficient than artificial light. An adjustable blade scrapes off the algae once it reaches a certain thickness.

“It’s like mowing the lawn. We just cut the top, and it keeps growing,” says Wen, adding that harvest may happen every two to three days in summer compared to once a week in winter.

Gross-Wen Technologies has experimented with turning harvested algae into slow-release fertilizer pellets for gardens and lawns. The founders say this, along with other potential applications like bioplastics, could give wastewater treatment facilities additional revenue streams.

Cost efficient and versatile

Data from at least 10 pilot projects across Iowa, Illinois, Kansas and Washington show the RAB system uses less energy than traditional wastewater systems. It’s also 10 times more efficient than other algae treatment options, largely due to its compact design. Taking up less than a tenth of a football field, the RAB system can recover one ton of nitrogen, half a ton of phosphorous and 16 tons of carbon dioxide each year.

Wen says the RAB system is also more cost-efficient than many alternatives, especially if it’s added to existing infrastructure. The central Iowa town of Slater estimates it will save roughly $1 million by choosing the RAB system for an upgrade to its municipal wastewater treatment plant. The current unit in Slater treats about one-third of the town’s wastewater needs. But later this year, Gross-Wen Technologies will expand the RAB system to serve the whole population, around 1,500 people.

Martin Gross, left, and Zhiyou Wen next to the RAB system. Photo courtesy of Gross-Wen Technologies.
Martin Gross, left, and Zhiyou Wen next to the RAB system. Photo courtesy of Gross-Wen Technologies

Wen adds that the RAB system is highly versatile to meet the needs of clients. Like Legos, more units can be added to treat higher volumes of wastewater or placed at different stages of treating wastewater.

“In Slater, the RAB system is treating wastewater before it’s discharged into a river. The pilot project in Chicago is treating a different wastewater stream; the RAB system is pulling out nutrients from water before it goes into the metro’s facility,” explains Wen.

Along with all of the household and commercial wastewater, the Metropolitan Water Reclamation District of Greater Chicago serves many large-scale food and beverage manufacturers. Coca Cola and Kellogg Company are just a few that produce high volumes of nutrient-rich wastewater. Wen says being part of the pre-treatment solution could reduce the burden on Chicago’s water district and help industries avoid higher surcharge rates.

Across the food supply chain, Iowa State researchers are striving to help protect the health of animals, people and the environment.

Iowa State University

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