Fig. 1. The protective effect of gut microbiota on S. aureus-induced mastitis.

Mammary gland tissues were harvested from untreated mice, gut microbiota-dysbiosis mice and FMT to gut microbiota-dysbiosis mice 24 h after infection with S. aureus (1 × 10⁵, 1 × 10⁶, and 1 × 10⁷ CFU). a Mammary gland tissue sections were stained with H & E (100×). The black arrow was the normal tissues. The red arrow was the infiltration of inflammatory cells. The blue arrow was the hyperplastic of alveolar wall. Levels of pro-inflammatory cytokines, including TNF-α (b), IL-1β (c), and IL-6 (d), and MPO activity (e) in mammary glands. f Levels of the tight junction proteins Occludin, Claudin-3, and ZO-1 in mammary glands. The results are presented as the mean ± SEM of three independent experiments (n = 6–8); *p < 0.05 is significantly different from each group.