Phenotypic PIA-Dependent Biofilm Production by Clinical Non-Typeable Is Not Associated with the Intensity of Inflammation in Mammary Gland: A Pilot Study Using Mouse Mastitis Model.

Non-typeable (NT) strains are associated with chronic bovine mastitis. This study investigates the impact of biofilm formation by clinical NT on cytokine production and mammary tissue damage by using a mouse mastitis model. Mice infected with two different NT strains with strong and weak biofilm forming potential demonstrated identical clinical symptoms (moderate), minimal inflammatory infiltrates, and tissue damage (level 1 histopathological changes) in the mammary glands. However, the load in the mammary glands of mice and the level of pro-inflammatory cytokines (IL-1β, IL-6, IL-12, IL-17 and IFN-γ) in serum were significantly higher ( ≤ 0.05) in those infected with the strong biofilm forming NT strain. The level of IL-6 in sera samples of these mice was extremely high (15,479.9 ± 532 Pg/mL). Furthermore, these mice died in 24h of post infection compared to 30 h in the weak biofilm forming NT infected group. The study demonstrates no association between the strength of PIA (polysaccharide intercellular adhesion)-dependent biofilm production by clinical NT and mammary gland pathology in a mouse mastitis model. However, the role of biofilm in the virulence of advancing the time of mortality in mice warrants further investigation.