Graduate Student Develops Method to Study Salmonella Transmission

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FAYETTEVILLE, Ark. — Yichao Yang, a graduate student in the Department of Poultry Science is analyzing how salmonella is transmitted within a chicken flock to find a way to prevent the spread of the major foodborne pathogen.

“My research work focuses on drawing an exact picture of how salmonella is transmitted when it is introduced into a chicken,” Yang said. “If we are able draw this picture very clearly, we can stop salmonella at an early stage, ensuring the safety of poultry products.”

She presented her findings last month at the American Society of Microbiology’s 115th meeting in New Orleans.

The Centers for Disease Control estimates that salmonella causes 1 million illnesses in the United States every year. Despite salmonella being recognized as a major foodborne pathogen, the mechanism by which the bacteria are transmitted within a poultry flock is still poorly understood.

Yang used genetically identifiable strains of the bacteria, allowing her to trace them as they spread from chicken to chicken and found that contrary to previous research, chickens can be infected by multiple strains at the same time.

To track transmission pathways, Yang constructed a set of six identical but genetically marked strains by inserting six random nucleotides into the chromosome of S.enteritidis, a strain of salmonella recognized for causing foodborne illnesses. The nucleotides made each strain traceable as they spread throughout the flock.

Yang and her adviser, Young Min Kwon, assistant professor in poultry science, designed three sets of experiments to track salmonella transmission. The first experiment introduced salmonella into chicks orally, the second added a low and a high dose of salmonella to the water supply and the third introduced salmonella by infecting the feed with the low and high doses.

Yang found that the strains were found after seven days in the chicks infected with high dose, whereas at 14 days nearly all the strains were identified in the chicks.  Yang’s data also showed that culled infection or mixed infection happened in each chick.

“This is a pretty big finding, and I did not recognize it at first because a major theory in the field of salmonella transmission — called the colonization inhibition theory — says that if one strain of salmonella infects a chick, a second strain cannot infect the chick, suggesting there might be unknown mechanisms involved,” Yang explained.

She plans to continue her research work by conducting bigger trial to study these findings in further detail.

About the University of Arkansas: The University of Arkansas provides an internationally competitive education for undergraduate and graduate students in more than 200 academic programs. The university contributes new knowledge, economic development, basic and applied research, and creative activity while also providing service to academic and professional disciplines. The Carnegie Foundation classifies the University of Arkansas among only 2 percent of universities in America that have the highest level of research activity. U.S. News & World Report ranks the University of Arkansas among its top American public research universities. Founded in 1871, the University of Arkansas comprises 10 colleges and schools and maintains a low student-to-faculty ratio that promotes personal attention and close mentoring.