Harmless strains of E. coli exist in the gastrointestinal tracts of all human beings. However, certain strains of E. coli are known for causing illnesses in humans. An Iowa State University researcher and her team of research post-docs and students sought out a link between food and extraintestinal pathogenic E. coli (ExPEC) infections. The research findings are published in the journals of Zoonoses Public Health and PLOS ONE.
Melha Mellata, assistant professor at Iowa State, began looking into how E. coli from chicken eggs and meat cause disease in humans and poultry while she was working at Arizona State University in 2011. Her research, funded by the United States Department of Agriculture (USDA), was a collaboration with Roy Curtiss III of Arizona State University (now at University of Florida), James R. Johnson of University of Minnesota and John M. Fairbrother of University of Montreal.
They wanted to find the source of ExPEC that causes infections outside the gastrointestinal tract in humans, namely sepsis, meningitis and urinary tract infections (UTI). Sepsis, a bacterial infection of the blood, is the 10th leading cause of death in the U.S., with 30 percent of the reported infections being caused by E. coli. Additionally, E. coli causes 80 percent of UTIs.
It is possible for ExPEC to be transferred to humans through the consumption of uncooked, undercooked or cross-contaminated foods or when it comes in contact with animals, such as chickens. Not only is the illness itself a bad thing, but treating it has become a challenge.
“ExPEC has increasingly become resistant to antibiotics used to treat infections. However, if we know the source of these bacteria, we could find the best ways to prevent them,” Mellata said.
Another problem with ExPEC, she said, is it can be detrimental to the poultry industry, causing a loss of chickens and costly sanitation efforts.
What Mellata and her fellow researchers discovered was that chicken eggs and meat can carry E. coli, including the ExPEC strain, that can cause human illness. Mellata said her team was the first to detect ExPEC in chicken eggs and to find that some ExPEC from food have the potential to cause UTI, meningitis and sepsis in humans. These diseases, when caused by ExPEC, can be especially dangerous to pregnant women and their newborns.
In 2015, when Mellata accepted her current position at Iowa State, she brought the remaining USDA funding and her research with her to continue pursuing. The continued research was made possible through the funding and by hiring research post-docs Zach Stromberg and Angelica Van Goor.
While at Iowa State, Mellata and her team of post-docs and students continued studying ExPEC, further looking into how it is transferred from seemingly healthy chickens to humans.
Through the use of a combination of genotypic, phenotypic and in vivo screenings, the researchers were able to determine the risks ExPEC from poultry poses to humans. What they discovered is that chicken feces could be a carrier of some ExPEC that causes diseases to both humans and chickens. When humans or chickens come in contact with the feces, they could become infected and become sick.
“Although I have previously worked on E. coli in cattle, I was not aware that poultry products could be contaminated with E. coli that has the potential to cause UTI and sepsis in humans,” Stromberg said. “This project further enhanced my knowledge on food safety and highlights the importance of safe handling and proper cooking practices.”
By better understanding what causes ExPEC to populate and contaminate food, scientists can develop ways to decrease its occurrence. This will help lead to improved consumer health through better animal production and food safety practices, Mellata said.
“My goal is to make people aware of this E. coli and how it can come from the foods we eat. People should not be scared of eating poultry products, because they are a good source of proteins and vitamins, but I want to make people aware of how to handle food safely to prevent them from getting a foodborne illness,” Mellata said.
Once additional funding is secured, the next step for Mellata and her researchers is to determine what genetic attributes make E. coli able to cause sickness in animals and humans. They also want to find improved ways to detect the E. coli in food and seemingly healthy animals.
Mellata is thankful to have received funding from the USDA to not only conduct this research, but to hire young researchers who will learn the importance of food safety research.
“Without this funding, we could not have involved these young students and post-docs,” Mellata said.