Study On The Immunological Protective Effect Of Two Lactobacillus Plantarum Against Staphylococcus Aureus Infection

Staphylococcus aureus is a common Gram-positive pathogen that induces the release of inflammatory cytokines and causes intestinal infections.We examined two strains of Lactobacillus plantarum suppressing mitogen protein kinase(MAPK)signaling pathway,cytokines TNF-? and IL-6 to regulate the inflammatory response,and its immune regulation function,as well as their impacts on intestinal microflora structure in mice infected with S.aureus.The experiment was divided into two parts.One was a cell experiment,in which macrophage RAW264.7 was used to establish an inflammation model with S.aureus,and single and mixed Lactobacillus plantarum were used for intervention.The levels of cytokines TNF-? and IL-6 in supernatant of the cells and their mRNA expression were detected by ELISA and real-time PCR,the protein levels of P38 and JNK were detected by Western blot.Another one was a mice experiment,Kunming female mice were divided into prevention group,treatment group and control group.S.aureus was infected for one week before or after treatment of mice with lactic acid bacteria,and the contents of IFN-? and IL-4 in the serum and the content of sIgA in intestinal contents during the experiment were measured.After collecting the feces of mice,the 16 S rRNA gene sequencing library of mouse intestinal microorganisms was constructed by using high-throughput sequencing technology.The bacterial flora,hierarchical distribution curve,heat map,dilution curve,Venn diagram,etc.,analysis of intestinal flora composition of mice in each group.The results showed that macrophages infected with S.aureus,the cell inflammatory cytokines TNF-? and IL-6 content increased significantly,after intervene with mixed Lactobacillus plantarum,the content of TNF-? and IL-6 and their mRNA expression were significantly decreased.At the protein level,Staphylococcus aureus significantly induced the phosphorylation of p38 and JNK proteins in RAW 264.7 macrophages,and Lactobacillus plantarum inhibited the phosphorylation of p38 and JNK proteins.After infected with S.aureus,the ratio of IFN-? / IL-4 in serum(especially in mixed lactic acid bacteria group)was significantly decreased from infection to convalescence.Secretion of sIgA in the intestinal contents of mice,especially mixed lactobacillus group(9.4-9.7 ?g/mL)was significantly higher than that of single lactic acid bacteria group.At the phylum level,the dominant phylum in the mouse gut microbiota was Firmicutes,Bacteroidetes,Proteobacteria.Therefore,the mixed Lactobacillus plantarum has good anti-inflammatory activity in vitro,increase the anti-inflammatory factor in mice and secretion of sIgA in the intestine,after infected with S.aureus,thereby inhibiting inflammation and regulating the structure of intestinal flora.