Faculty at the University of Florida are exploring an alternative treatment for infections from an unlikely source: crustaceans. The shells of lobster, shrimp and crab are treated with an alkaline substance such as sodium hydroxide to produce chitosan (pronounced ky-to-san), a fibrous sugar with a chemical structure similar to cellulose.
Chitosan microparticles are then engineered through a chemical process developed by Kwangcheol “Casey” Jeong, an assistant professor of microbiology and food safety in the Emerging Pathogens Institute at the University of Florida.
“The main appeal of chitosan microparticles is that it has broad-spectrum anti-microbial activity,” explains Dr. Klibs N.A. Galvao, an associate professor at the University of Florida’s College of Veterinary Medicine. Therefore, it could be used to treat a variety of illnesses in dairy cows such as metritis and mastitis. Furthermore, Galvao says, “It does not lead to antibiotic resistance because of the way it acts on the bacteria cell wall quickly.”
Metritis, a bacterial infection of the uterus, is one of the most common diseases for dairy cattle. Affecting as many as 25 percent of U.S. dairy cows, metritis costs nearly $400 per case in lost productivity and treatment costs, according to Cornell University.
Mastitis is even more prevalent than metritis and is widely considered to be the most costly disease of dairy cattle, exceeding $1 billion annually based on work by the National Mastitis Council.
Both diseases significantly affect the dairy producer’s bottom line. And together they are the largest cause of antibiotic use on farms, giving rise to increasing concern of antibiotic resistance.
Chitosan microparticles
Anti-microbial research on chitosan began more than 30 years ago. Today, it is widely regarded as a bacteriocidal, which means that it kills bacteria.
Developing the chitosan treatment has been a team effort.
“Dr. Galvao and I work very closely,” Jeong explains. “My team developed chitosan microparticles and figured out anti-microbial activity, and Dr. Galvao’s team has found that chitosan microparticles kill pathogens in uterus.”
While Jeong’s lab has focused on basic research, Galvao’s work is translating the science into real-world application for the dairy industry. “We are invaluable collaborators for each other,” Jeong says.
Jeong’s USDA-funded research had already shown chitosan microparticles could be used to eliminate pathogenic E. coli from the G.I. tract of cattle. Because E. coli is believed to have an important role in the development of metritis, the researchers began using chitosan microparticles to both prevent and treat metritis in dairy cattle.
“Chitosan microparticles work by killing the bacteria in the uterus,” Galvao explains. Although the mechanism is not completely known, these microparticles bind to bacterial cells and directly affect the permeability of the outer membrane.
In simple terms, once the membrane is damaged by the microparticles, intracellular components leak out and the bacterial cell dies. The infection stops spreading and is eventually eradicated.
Other advantages of chitosan include high biodegradability and non-toxicity. It is both ecologically friendly and one of the most abundant natural materials in the world. When used as directed, it has not shown harm to people, pets, wildlife or the environment. The use of chitosan microparticles for organic dairies could also be a powerful asset.
Treatment
“Because chitosan microparticles work by direct contact with bacteria, we have to deliver chitosan microparticles to where the bacteria are,” Galvao says. In the case of metritis, chitosan microparticles are infused into the uterus. With mastitis, the treatment is infused into the udder through a teat.
Treatment consisted of daily infusions for five days. However, the researchers noted that extending the duration of infusions may further increase effectiveness.
“The administration only takes a few minutes, but we have to make sure we do not introduce more bacteria while infusing chitosan microparticles,” Galvao cautions. Thorough cleaning of the vulva for metritis treatment, or the teat for mastitis, is essential.
A research trial with this technique was conducted at North Florida Holsteins of Bell, Florida, 30 miles from the University of Florida. Owner Don Bennink maintains a herd of 10,000 registered Holsteins, and he has been involved in research trials most of the 36 years North Florida Holsteins has been in operation.
“Our research has involved both university and corporate groups,” Bennink says. “Some major private trials were done to get FDA and USDA approval for various products, and a fair number of students get their masters and Ph.D. degrees from the trials on an annual basis.”
While Bennink’s farm hosted the chitosan microparticle trial, and his team administered the treatments, he can’t comment directly on the results he observed. “We make a point that studies of this sort are totally blind to us,” he explains. “Neither I nor any of our people know treatment or control animals. The final result will not be influenced by us.”
Hosting on-farm research challenges the normal routines of North Florida Holsteins and often calls for extra effort, such as the microparticle infusions. But Bennink believes the efforts are worthwhile. “You need to have the desire to find better practices and expose your personnel to the opportunity to better themselves,” he points out.
“The effort has improved our practices and made many great friends.” Should the research prove positive, Bennink knows firsthand the potential value. “The opportunity to reduce the use of antibiotics will be a great reward,” he says.
Commercial use
“To date, we have published four research articles,” Galvao says. “We have shown that chitosan microparticles are safe and exert broad-spectrum antibiotic activity without leading to antibiotic resistance.” The researchers’ work shows great promise for the prevention of metritis in dairy cows, and the treatment is especially effective against antibiotic-resistant micro-organisms.
And the cost, though prohibitive currently, may be decreasing enough in the future to be applicable on a large scale.
“The treatment right now costs around $200 because we manufacture the microparticles in the lab,” Galvao explains. “This method is very labor-intensive so most of the cost, approximately 85 percent, is labor. If we can scale up production, the cost could be reduced dramatically to around $30, which would be very competitive.”
One of the most remarkable aspects of the treatment potential is that chitosan itself is not a new discovery. The compound is already used in numerous ways with food, cosmetic, agricultural and biomedical applications. Chitosan film is an edible coating used to double the shelf life of food. It is used in the manufacturing of cheese, wine and beer.
Chitosan supplements are available as over-the-counter supplements for human consumption. And the U.S. military is using chitosan bandages to reduce bleeding and promote faster wound healing, especially with burns.
Chitosan is also used to treat Crohn’s disease, dental inflammation, breast cancer and reduce scar formation after plastic surgery. It is used as a plant bio-pesticide for fungal infections and already serves as a seed coating for cotton, corn, soybeans, wheat and many other seeds.
Chitosan extends the life of both cut flowers and Christmas trees, and has been a component of NASA plant research aboard the Mir Space Station. Both the EPA and the USDA already regulate chitosan use and application.
Galvao and Jeong are currently doing a large trial to further evaluate chitosan microparticles’ effectiveness. “The main thing now is to show that it actually works out in the real world,” Galvao shares. The researchers will soon start additional trials evaluating the efficacy of chitosan microparticles in treating mastitis in dairy cows.
“After that, we will have to develop partnerships with commercial companies that would be interested in manufacturing chitosan microparticles for commercial use.” 
PHOTO: In the case of metritis, chitosan microparticles are infused into the uterus. Treatment occurs daily for five days and takes only a few minutes. Photo provided by Dr. Klibs Galvao, University of Florida, College of Veterinary Medicine.
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Karena Elliott
- Freelance Writer
- Amarillo, Texas
