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Enterococci resistance is increasing sharply, which poses a serious threat to public health. Rhamnolipids are a kind of amphiphilic compound used for its bioactivities, while the combination of nontraditional drugs to restore linezolid activity is an attractive strategy to treat infections caused by these pathogens. This study aimed to investigate the activity of linezolid in combination with the rhamnolipids against Enterococcus faecium. Here, we determined that the rhamnolipids could enhance the efficacy of linezolid against enterococci infections by a checkerboard MIC assay, a time–kill assay, a combined disk test, an anti-biofilm assay, molecular simulation dynamics, and mouse infection models. We identified that the combination of rhamnolipids and linezolid restored the linezolid sensitivity. Anti-biofilm experiments show that our new scheme can effectively inhibit biofilm generation. The mouse infection model demonstrated that the combination therapy significantly reduced the bacterial load in the feces, colons, and kidneys following subcutaneous administration. This study showed that rhamnolipids could play a synergistic role with linezolid against Enterococcus. Our combined agents could be appealing candidates for developing new combinatorial agents to restore antibiotic efficacy in the treatment of linezolid-resistant Enterococcus infections. [ABSTRACT FROM AUTHOR]

Abstract Biosurfactants (BS) are amphipathic compounds produced by diverse groups of microorganisms exhibiting various biological activities. The current study aimed to assess antimicrobial, anti-adhesive and anti-biofilm activities of BS isolated from lactic acid bacteria (LAB), including Pediococcus acidilactici and Lactobacillus plantarum against Staphylococcus aureus CMCC 26003 in vitro. Cell-bound BS from both Pediococcus acidilactici and Lactobacillus plantarum were extracted, and their surface activities were evaluated by oil spreading assay. As quantified by crystal violet method, BS inhibited adhesion and biofilm formation of Staphylococcus aureus in a dose-dependent manner. The above findings were further supported by results of scanning electron microscopy. These two kinds of BS affect expressions of biofilm-related genes (cidA, icaA, dltB, agrA, sortaseA and sarA) and interfere with the release of signaling molecules (AI-2) in quorum sensing systems. Biological activities observed for BS produced by tested LAB suggest prospects for their use against Staphylococcus aureus biofilm-related infections. Highlights • Crude BS produced by L. plantarum and P. acidilactici has good anti-adhesion and anti-biofilm activity against S. aureus. • The expression of genes related to biofilm formation (cidA, icaA, dltB, agrA, sortaseA and sarA) is affected by crude BS. • Crude BS interfere with the release of signaling molecules (AI-2) in quorum sensing systems. • BS can be used as special anti-bacterial biofilm biologicals, but has minimal effect on bacterial growth. [ABSTRACT FROM AUTHOR]