PSVIII-18 Protective effect of Lactobacillus Casei Zhang on E. coli induced mastitis in mice

Abstract Mastitis is an acute, obvious and harmful clinical disease in mammals. It is also one of the productive diseases with high incidence, rapid epidemic and great economic loss in dairy farming. Antibiotics are the first choice for the treatment of infectious mastitis, but the long-term use of antibiotics in large quantities will lead to the emergence of antibiotic residues and bacterial resistance, which is harmful to the health of both human and animals. As a potential substitute of antibiotics, Lactobacillus has great potential in the control of pathogenic microorganisms. The purpose of this study was to explore the effect of Lactobacillus casei Zhang (L. Casei Zhang) on the prevention of E. coli-induced mastitis in mice and its protective effect on the damage of the blood and milk barrier. Intramammary administration of E. coli was used to establish a mouse mastitis model. Control group (PBS), E. coli administration group, and L. casei Zhang pretreatment plus E. coli administration group were set up respectively and the mammary gland samples were collected for analysis. The results showed that: L. casei Zhang could significantly reduce the degree of breast tissue damage and the content of inflammatory factors TNF-α，IL-6 and IL-1β (P < 0.05). In addition, the expression of tight junction proteins ZO-1, Claudin-3 and Occludin in the mammary gland tissues of mice was significantly promoted (P < 0.05). In conclusion, intramammary administration of L. casei Zhang could effectively reduce the inflammation of the mouse mammary gland induced by E. coli, and this protection is achieved by promoting the expression of the blood-milk barrier tight junction proteins.