Methicillin-resistant Staphylococcus aureus (MRSA) is a highly pathogenic bacterium for which safe and effective prevention as well as treatment methods are currently lacking. In this study, Rhizoctonia bicornis S10 was isolated from Schisandra chinensis and used to inhibit MRSA. Through single-factor experiments and response surface methodology, the optimal culture medium and fermentation conditions for Rhizoctonia bicornis S10 were determined. The results demonstrated that optimal growth conditions for Rhizoctonia bicornis S10 were achieved using corn meal as the culture medium. Furthermore, the extract of Rhizoctonia bicornis S10 showed maximal inhibitory activity against MRSA under the following optimized conditions: moisture content of 150%, time of 2.5 d, temperature of 30 °C, and pH 5.0. Antagonistic experiments demonstrated that the crude extract of Rhizoctonia bicornis S10 exhibits significant inhibitory activity against MRSA. During the growth of MRSA, the crude extract effectively suppressed its proliferation. Measurements of alkaline proteinase and membrane potential confirmed the disruption of the MRSA cell membrane, which was further visually validated by scanning electron microscopy. Additionally, the crude extract was shown to inhibit the formation of MRSA biofilms. These findings suggest that Rhizoctonia bicornis S10 should hold promise as a novel approach for the prevention and treatment of MRSA infections, providing new strategies and insights for combating this pathogen.

Klebsiella pneumoniae is the second-most common opportunistic pathogen in clinical practice and has developed resistance to potent antibacterial drugs such as carbapenems. Therefore, developing safe and effective strategies for the prevention and treatment of K. pneumoniae infections remains a critical challenge. In this study, a strain named Tie-10 isolated from Antarctic samples demonstrated potent antibacterial activity against K. pneumoniae, which was subsequently identified as Bacillus nakamurai. The fermentation medium and culture conditions were systematically optimized through single-factor experiments, orthogonal array testing, and response surface methodology. The optimal medium composition was determined to be beef extract, peptone, and KNO₃. The culture conditions included a time of 24 h, temperature of 37 °C, pH of 7.0, and bottling volume of 80 mL. Antagonistic experiments demonstrated that the crude extract of B. nakamurai Tie-10 exhibited significant inhibitory activity against K. pneumoniae. The alkaline protease (AKP) assay demonstrated that the crude extract effectively disrupted the cellular integrity of K. pneumoniae, a finding further corroborated by scanning electron microscopy (SEM) analysis. Furthermore, the crude extract significantly inhibited extracellular protease secretion in K. pneumoniae, downregulated the expression of virulence-associated genes, and effectively disrupted biofilm formation. The study presented innovative strategies for the management and containment of K. pneumoniae infections.