Probiotic Characterization of Lactiplantibacillus paraplantarum SDN1.2 and Its Anti-Inflammatory Effect on Klebsiella pneumoniae-Infected Mammary Glands

<i>K. pneumoniae</i> is a major cause of bovine mastitis worldwide, making it difficult to control due to its resistance to multiple drugs. <i>L. paraplantarum</i> has been explored as a promising new approach to fighting bovine mastitis. In this study, the probiotic potential and safety of <i>L. paraplantarum</i> SDN1.2, as well as its ex vivo and in vivo anti-inflammatory effects against <i>K. pneumoniae</i>-induced mastitis, were comprehensively investigated using bioinformatics analyses and experimental validation methods. The results revealed that <i>L. paraplantarum</i> SDN1.2 exhibits non-hemolytic activity, is not cytotoxic, lacks virulence genes (e.g., adhesion factors, toxins, and invasion factors) and antibiotic resistance genes (e.g., beta-lactamases and tetracycline resistance genes), as supported by whole-genome sequencing, and significantly inhibits the growth of <i>K. pneumoniae</i>, as evaluated by antimicrobial tests. Following further validation in vitro, <i>L. paraplantarum</i> SDN1.2 demonstrated the capability to inhibit the adhesion and invasion of <i>K. pneumoniae</i> to bMECs. In a mouse model of <i>K. pneumoniae</i>-induced mastitis, <i>L. paraplantarum</i> SDN1.2 reduced the extent of neutrophil infiltration and inflammatory lesions. Furthermore, <i>L. paraplantarum</i> SDN1.2 pretreatment significantly reduced myeloperoxidase (MPO) activity and the expression of inflammatory cytokines (<i>IL-6</i>, <i>IL-1β</i>, and <i>TNF-a</i>) in mouse mammary gland tissue. In <i>K. pneumoniae</i>-infected bMECs, <i>L. paraplantarum</i> SDN1.2 significantly lowered lactate dehydrogenase (LDH) levels and expression of inflammatory cytokines such as <i>IL-6</i>, <i>IL-1β</i>, and <i>TNF-α</i>. The results demonstrated that the newly isolated <i>L. paraplantarum</i> SDN1.2 from bovine sources exhibits promising characteristics as a safe probiotic for the alleviation of bovine mastitis due to its safety profile and anti-inflammatory and antibacterial properties.