Biofilms on Dairy Farms

Chances are that you have touched, observed, or otherwise been plagued by a biofilm on your dairy farm. A biofilm is an aggregation of bacteria that are embedded in an extracellular polymeric substance (EPS) matrix. This matrix allows the bacteria to adhere to a surface. We might think of it as building a fort in which the bacterial colony is established, protected, fed, and allowed to thrive. The matrix traps particles and facilitates the exchange of DNA. Biofilms adhere to both living and non-living surfaces, posing a concern across many aspects of the dairy industry. Biofilms lead to contamination when they shed cells or bits of the EPS matrix that shear off. Protection from sanitizers and antimicrobial agents is provided to bacteria incorporated into a biofilm. Biofilms may be heterogeneous, meaning they are composed of multiple species of microorganisms, or they may be composed of a single type of organism.

Many producers are aware that biofilms can form on milking equipment and in tanks. Many materials, including plastic, glass, stainless steel, and others, serve as attachment surfaces for biofilms. Raw milk provides an ideal medium to facilitate the formation of a biofilm as it contains bacteria and is nutrient-rich. Another common place to find a biofilm on a dairy farm is in a watering cup or watering trough. The aqueous environment on the side of a trough or watering cup is often overlooked during cleaning or cleaned less frequently than desired. Cows introduce bacteria and organic matter into the water each time they drink, providing a prime environment for biofilm formation when temperatures are warm and water flow is low.

More recently, an aspect of biofilm formation that has attracted researchers' attention is its role in animal health. Many species of bacteria form biofilms or are harbored within biofilms that are produced by other microorganisms. Some of these bacteria are pathogenic to humans or animals. Researchers have determined that isolates of Staphylococcus aureus capable of producing biofilms are linked to chronic mastitis in dairy cows. The biofilm aids in protecting the pathogen from defenses put forth by the cow's body and also increases resistance to antimicrobial agents. To combat intramammary infections due to S. aureus, producers can talk to their veterinarian about vaccines (Raza et al. 2013), along with practicing good sanitation, proper management of infected cows, and following recommended milking practices.

A group of Canadian researchers recently examined genes that characterize intramammary infections caused by S. aureus (Veh et al. 2015). Their findings indicate that S. aureus strains that persist through the dry period produce more biofilm than those that do not. These results demonstrate the importance of biofilm formation as a survival strategy of this infection-causing bacterium. In contrast, other species of staphylococci, called coagulase-negative staphylococci (CNS), may form biofilms, but a recent review encompassing many studies reported inconclusive evidence that biofilm formation predicts intramammary infections (Vanderhaeghen et al. 2014).

References

• Raza, A., Muhammad, G., Sharif, S., and A. Atta. 2013. Biofilm producing Staphylococcus aureus and bovine mastitis: a review. Molecular Microbiology Research (online). 3(1):1-8.
• Vanderhaeghen, W., Peipers, S., Leroy, F., Van Coillie, E., Haesebrouck, F., and S. De Vliegher. 2014. Invited review: Effect, persistence, and virulence of coagulase-negative Staphylococcus species associated with ruminant udder health. J. Dairy Sci. 97(9):5275-5293.
• Veh, K. A., Klein, R. C., Ster, C., Keefe, G., Lacasse, P., Scholl, D., Roy, J. -P., Haine, D., Dufour, S., Talbot, B. G., Ribon, A. O. B., and F. Malouin. 2015. Genotypic and phenotypic characterization of Staphylococcus aureus causing persistent and nonpersistent subclinical bovine intramammary infections during lactation or the dry period. J. Dairy Sci. 98:155-168.