Primer sequences for qRT-PCR.

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen that can cause severe bacterial pneumonia. Amygdalin is the main active pharmaceutical ingredient of bitter almond, which has broad-spectrum antibacterial, anti-inflammatory, anti-oxidation and immunomodulatory effects. It is also the main ingredient of Yinhua Pinggan granule, which is commonly used to moisten the lung and relieve cough. However, little is known about the effects of amygdalin on MRSA. In this study, we found that amygdalin exhibited good antimicrobial activity in vitro against MRSA. Amygdalin has a protective effect on MRSA infected cells, and the effect is better when combined with levofloxacin. It also can reduce the adhesion and invasion of MRSA to cells. Amygdalin has anti-inflammatory and antioxidant effects, which can significantly reduce the increase of inflammatory factors and the production of ROS caused by infection. The protective mechanism of amygdalin on cells may be related to inhibiting the expression of NLRP3, ASC and IL-1β pyroptosis pathways. Taken together, our study suggests that amygdalin exerts antibacterial effects by affecting biofilm formation, the expression of virulence factors, and drug resistance genes. Amygdalin combined with levofloxacin has a protective effect on A549 cells infected with MRSA, and the mechanism may be related to the inhibition of inflammatory response, oxidative damage and pyroptosis.

耐甲氧西林金黄色葡萄球菌（Methicillin-resistant Staphylococcus aureus，MRSA）是一种条件致病菌，可引发严重的细菌性肺炎。苦杏仁苷（Amygdalin）是苦杏仁的主要药用活性成分，具备广谱抗菌、抗炎、抗氧化及免疫调节作用，同时也是常用于润肺止咳的银花平肝颗粒（Yinhua Pinggan granule）的核心成分。然而，目前关于苦杏仁苷对MRSA的作用效果仍知之甚少。本研究发现，苦杏仁苷在体外对MRSA展现出良好的抗菌活性。苦杏仁苷对MRSA感染的细胞具有保护作用，且与左氧氟沙星（levofloxacin）联合使用时效果更优；同时可降低MRSA对细胞的黏附与侵袭能力。此外，苦杏仁苷具备抗炎与抗氧化功效，能够显著抑制感染诱导的炎症因子升高及活性氧（Reactive Oxygen Species, ROS）生成。苦杏仁苷对细胞的保护机制可能与抑制NLRP3、ASC及IL-1β细胞焦亡通路的表达有关。综上，本研究表明苦杏仁苷可通过影响生物被膜形成、毒力因子表达及耐药基因的表达发挥抗菌作用。苦杏仁苷与左氧氟沙星联合使用对MRSA感染的A549细胞具有保护作用，其机制可能与抑制炎症反应、氧化损伤及细胞焦亡相关。