August 21, 2019: EPI investigator KC Jeong aims to uncover the next generation of antimicrobials. From his microbiology lab to an experimental farm, his research explores how food animals are affected by novel and drug-resistant pathogens — and what kills them.
Drug-resistant bacteria are a metastasizing global menace. For the past seventy-five years, roughly since Franklin D. Roosevelt signed the GI Bill of Rights, society has enjoyed a wondrous time span where powerful antibiotic drugs allowed medical practitioners to aggressively fight a broad array of common bacterial infections.
But the golden years of antibiotics are waning, and many of the bugs they have reliably killed now have genes that allow them to resist our medicines unscathed. Drug-resistant tuberculosis and pneumonia, methicillin-resistant Staphylococcus aureus (MRSA), and pathogenic E. coli, Shigella, and Salmonella — these terms were once relegated to technical medical conversations but are now commonly heard on the nightly news.
UF’s Emerging Pathogens Institute investigator KC Jeong is focused on uncovering novel ways of controlling disease-causing microorganisms in farmed animals, as well as learning how these tiniest of bits of life are outwitting humanity’s best minds.
When Jeong arrived to the University of Florida in 2011, he had recently completed a PhD at the University of Wisconsin-Madison, where he investigated novel ways of eliminating the threat of E. coli O157:H7 — a highly virulent, and sometimes fatal, cause of food poisoning — from beef. While testing a passive antibody-based immune therapy, Jeong discovered that the substance used to deliver the antibodies, chitosan nanoparticles, harbored powerful antimicrobial activities. Chitosan is a sugar found in the hard outer shells of shrimp and other crustaceans. Nanoparticles are bits of miniscule matter that measure between 1 and 100 nanometers long.
“Chitosan nanoparticles are often used to deliver drugs to targeted sites, but before our study, nobody knew that they had antimicrobial activity by themselves,” Jeong recalls. “It was such a surprise, you don’t expect to get meaningful data from your control group.” Researchers already knew that chitosan in its raw form had antimicrobial properties under certain conditions, but no one had yet looked into its properties when it’s engineered into micro-sized particles; which is important, because microparticles will sometimes behave entirely differently from their parent material.
The chance discovery landed Jeong on EPI’s radar, and he was recruited with a position split between the EPI and UF’s Institute of Food and Agricultural Sciences animal sciences department. First on his agenda? Figuring out why chitosan nanoparticles are so good at killing pathogenic E. coli O157:H7.
KC Jeong in his EPI microbiology lab.
Using genetics and animals, he soon discovered that the miniature chitosan bits essentially plug up “gates” in an E. coli’s bacterial cell wall that provide a portal to accept nutrients. The structure of the E. coli bacterium’s cell wall is also disrupted by the particles, causing further damage and death.
Jeong and his collaborators found that chitosan nanoparticles turned out to be broadly effective against many other disease-causing microorganisms too. Better yet, they did not produce resistance in the bacteria targeted. Jeong’s further work revealed chitosan nanoparticles reduced the presence of various strains of Salmonella enterica in agricultural water. This was eye-opening because livestock can acquire this disease-causing bacteria from drinking water, and then pass it on to people when the animals become food.
But not all particles are created equal, so Jeong studied how to best engineer chitosan nanoparticles to optimize their effectiveness against E. coli O157:H7 without producing resistance. Creating particles smaller than 300 nanometers, and adding other ingredients, turned out to be key.
“It kills bacteria very quickly, like Clorox,” says Jeong. “The beauty of this is that it does not cause antibiotic resistance. It disru