Anti-Inflammatory Effects of Weissella cibaria SDS2.1 Against Klebsiella pneumoniae-Induced Mammary Gland Inflammation

Dairy cows are highly susceptible to mastitis caused by <i>Klebsiella pneumoniae</i>, and treating these infections poses a challenge due to the resistance of the bacterium to common antibiotics. This study aimed to evaluate the safety of <i>W. cibaria</i> SDS2.1 and investigate its protective effects against <i>K. pneumoniae</i>-induced mastitis. The safety of <i>W. cibaria</i> SDS2.1 was assessed through comprehensive analyses, including antibiotic resistance profiling, hemolysis assays, cell cytotoxicity tests, and whole-genome sequencing. Furthermore, its ability to protect against cellular and tissue damage caused by <i>K. pneumoniae</i>-induced mastitis was evaluated using both in vitro and in vivo models. Our results revealed that <i>W. cibaria</i> SDS2.1 was non-hemolytic, non-cytotoxic, and significantly inhibited the growth of <i>K. pneumoniae</i> (<i>p</i> < 0.05). Additionally, <i>W. cibaria</i> SDS2.1 effectively reduced the adhesion and invasion of <i>K. pneumoniae</i>. In the <i>K. pneumoniae</i>-induced mouse mastitis model, <i>W. cibaria</i> SDS2.1 significantly reduced myeloperoxidase (MPO) activity, mammary tissue damage, and the expression of inflammatory cytokines (IL-6, IL-1β, and TNF-α) (<i>p</i> < 0.05). In <i>K. pneumoniae</i>-infected bovine mammary epithelial cells (bMECs), <i>W. cibaria</i> SDS2.1 significantly decreased lactate dehydrogenase (LDH) release, indicating reduced cellular damage. These findings demonstrate that <i>W. cibaria</i> SDS2.1 exhibits anti-inflammatory properties in experimental models, suggesting its potential role in mitigating <i>K. pneumoniae</i>-induced mastitis.