Staphylococcus aureus accessory gene regulatory Quorum Sensing (QS) system facilitates biofilm formation and biofilms are major contributors for antimicrobial resistance. Quorum quenchers could be used as an adjunct to antibiotics to reduce the development of drug resistance. The objective of this study was to evaluate the sub-inhibitory concentration of ethanolic extracts of Mango Seed Kernel Extract (MSKE), Guava Leaf Extract (GLE) and ε-Polylysine (ε-PL) against quorum sensing mediated virulence factors of S. aureus.
    We evaluated the antibacterial and Quorum Quenching (QQ) activity of these compounds on 10 MRSA and 10 MSSA isolates. The antibacterial activity was tested by disc diffusion assay. The Minimum Inhibitory Concentrations (MIC) for MRSA isolates were: 20 µg/mL for ε-Polylysine, 20 µg/mL for MSKE extract and GLE and for MSSA isolates were: 12.5 µg/mL for ε-Polylysine, 20 µg/mL for MSKE extract and GLE. Quorum Sensing Inhibition (QSI) activity was determined at sub-MIC of 10 µg/mL of all the compounds by studying inhibition of the delta hemolysin on sheep blood agar plate and motility on soft agar media. All these compounds affected the motility and expression of δ-hemolysin activity which confirms that these compounds interfere with the QS activity. The QQ effect was confirmed by quantitation of hld (delta hemolysin) transcript and rnaIII transcript by qPCR. The results of this study will be presented as proof of QQ activity by ε-PL, MSKE, and GLE on S. aureus in general and MRSA in particular, as an attractive proposition for adjunct therapy and anti-virulence therapy of MRSA infections.

中文翻译：

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群体猝灭作为治疗耐甲氧西林金黄色葡萄球菌（MRSA）的策略-ε-聚赖氨酸，番石榴叶乙醇提取物和芒果种子仁的作用

金黄色葡萄球菌辅助基因调控群体感应（QS）系统促进生物膜的形成，生物膜是抗菌素耐药性的主要贡献者。群体猝灭剂可以用作抗生素的辅助剂，以减少耐药性的发展。这项研究的目的是评估芒果籽仁提取物（MSKE），番石榴叶提取物（GLE）和ε-聚赖氨酸（ε-PL）的乙醇提取物对群体感应介导的金黄色葡萄球菌毒力因子的亚抑制浓度。。
    我们评估了这些化合物对10个MRSA和10个MSSA分离物的抗菌和法定猝灭（QQ）活性。通过盘扩散测定法测试抗菌活性。MRSA分离物的最低抑菌浓度（MIC）为：ε-聚赖氨酸为20 µg / mL，MSKE提取物和GLE的为20 µg / mL，MSSA分离物为：ε-聚赖氨酸为12.5 µg / mL，ε-聚赖氨酸为20 µg / mL MSKE提取物和GLE。通过研究对羊血琼脂平板上的溶血素溶血素的抑制作用和在软琼脂培养基上的运动性，在所有化合物的亚MIC下测定群体感应抑制（QSI）的活性为10 µg / mL。所有这些化合物都影响δ-溶血素活性的运动性和表达，这证实了这些化合物干扰了QS活性。通过hld定量证实了QQ效应qPCR检测（δ溶血素）转录本和rnaIII转录本。这项研究的结果将作为ε-PL，MSKE和GLE对金黄色葡萄球菌，特别是MRSA的QQ活性的证明，作为MRSA感染的辅助治疗和抗毒力治疗的有吸引力的主张。