Bacterial endometritis (inflammation of the lining of the uterus, called the endometrium) is a common cause of infertility in broodmares. Unfortunately, it can also be a challenging condition to treat due to the bacteria forming biofilms (a group of bacteria surrounded by a matrix that is protected from the host immune system and antibiotic treatment) or becoming dormant.

Due to the significant costs of treating biofilms (in humans, an estimated $1 billion annually), equine researchers have recently begun studying biofilms’ role in chronic infections to better learn how to combat them. Ryan Ferris, DVM, MS, Dipl. ACT, an assistant professor at Colorado State University’s Equine Reproduction Laboratory, in Fort Collins, described biofilms in detail and his methods for eradicating them during the 2016 Theriogenology Conference, held July 27-30 in Asheville, North Carolina.

“Bacteria live two different lifestyles: as single free-floating cells and as a community in a biofilm,” Ferris explained, adding that the latter can adapt to their uterine environment and are resistant to traditional antibiotic treatments.

The single free-floating bacteria cause acute infections that are easily treated with antibiotics, whereas biofilms establish chronic infections tolerant to antibiotics and protected from the phagocytes the body uses to engulf and kill bacteria.

So how do these biofilms form in the first place?

“It all starts as an acute infection,” said Ferris. “The bacteria floating around the (uterine) environment begin to attach to sites through adhesion proteins. As more and more bacteria attach to