Probio-M9, a breast milk-originated probiotic, alleviates mastitis and enhances antibiotic efficacy: Insights into the gut–mammary axis

Abstract

Breast milk naturally contains lactic acid bacteria, but their precise origin remains a subject of debate. In this study, we utilized a rat mastitis animal model to investigate the potential of a breast milk-derived probiotic strain, Lacticaseibacillus rhamnosus Probio-M9, in alleviating mastitis and enhancing the efficacy of antibiotic treatment. Through histopathological analysis of mammary tissue, we observed that Probio-M9 effectively relieved mastitis, mitigated inflammation, and improved the response to antibiotic treatment. Metagenomic analysis further revealed that Probio-M9 enhanced interactions among gut microbes, accompanied by an increase in the relative abundance of Ruminococcaceae and the regulation of specific genes and carbohydrate-active enzymes, subsequently impacting host immunity. Additionally, an intriguing finding was the translocation of live Probio-M9 from the gut to the mammary tissue only during bacterial mastitis and lactation, likely facilitated through lymphatic circulation. These findings advance our understanding of the intricate gut–mammary axis and provide valuable insights into the potential health benefits of probiotic interventions.