 but drug-reistant bacteria threaten their usefulness. Jeong intends to test if combining them with specific nanoparticles will extend their effectiveness.
“Our work is innovative and significant because outcomes of this project are expected to lead to practical, effective new treatment options using nanotechnology,” Jeong says. “Overall, we expect that development of the new, value-added nano-antimicrobials will help improve animal and human health.”
While the trend amongst locavores is “farm to table,” Jeong’s research takes him on a less traveled path from laboratory to farm and back again. A significant part of his research agenda has focused on learning how beef cattle acquire pathogenic E. coli and antibiotic resistant bacteria.
“Our findings show that even animals grown without exposure to antibiotics, animals that have no history of antibiotic use in their feed or for treating infections, they have some baseline of antibiotic resistant bacteria in their gastro-intestinal tracts,” Jeong says. “Which led us to ask, ‘How did it get there?’” That seemingly simple question has led to more than $2.2 million in funding for his research between 2015 and 2020 from the U.S. Department of Agriculture.
Often working with EPI Director John G. Morris, and EPI researchers Judith Johnson and Volker Mai, Jeong’s team sampled a network of northcentral Florida farms to tease out whether antibiotic-resistant bacteria found in grass-fed cows originates in the environment (soil or water), or if it is a natural component of healthy cows’ intestinal microbiota. They identified nine bacterial isolates resistant to cefotaxime (a type of cephalosporin), six of which were identical to those found in people, and many of which also harbored high levels of multi-drug resistance.
Another of Jeong’s studies revealed that beef cattle, sampled every three months after birth, are colonized with Shiga toxin-producing E. coli within their first year of life. This is a particularly virulent strain of E. coli, and learning how it gets into cows could help mitigate its prevalence and reduce the nearly 250,000 cases of food-borne illness it causes in the U.S. alone annually. The colonization is hypothesized to occur from older cows, and the presence of this bacteria is linked with a lower diversity of gut microflora in young calves; however, their diversity then increases as they age.
“We think that the younger calves tend to have a higher burden of these disease-causing pathogens compared to older cows simply because their immune systems and GI-tract microbiota are immature,” Jeong says. “We hypothesize that as the calves age and their immune systems mature, it learns to kick out the harmful bacteria, leading to a healthier microflora composition.”
KC Jeong, far right, and his laboratory research team: (from left to right) visiting scholar Haitao Yu, PhD student Peixin Fan, post-doctoral researcher Zhengxin Ma, and PhD students Lin Teng, Shinyoung Lee and Ting Lui.
Similar to the E. coli study, Jeong’s lab discovered that beef calves become colonized with cephalosporin-resistant bacteria in their GI tract even when they are raised without the use of antibiotics. Conventional dogma dictates that overuse of antibiotics in agricultural and large-animal veterinary contexts has driven the rapid increase in antibiotic resistant bacteria in farm animals through selective pressures. But Jeong’s research into animals free of antibiotic exposure acquiring resistant bacteria points to an important alternative pathway: they also get it from the environment.
Building on this study, his lab next sampled soil and agricultural water sources on the affected farms and found cefotaxime-resistant bacteria to be highly prevalent. By analyzing fecal samples from cattle, and environmental samples from 17 different farms, and combining the findings with a survey of husbandry practices, his team uncovered some fascinating trends. They found that 98.7 percent of the soil samples contained the resistant bacteria, as did 95.7 percent of the forage, and 88.6 percent of the water sa