传统发酵食品中分离的乳酸菌粗提物对耐甲氧西林金黄色葡萄球菌抑菌机制研究

目的 探究乳酸菌HS011 (Lactobacillus plantarum MG5276)、德氏乳杆菌保加利亚亚种HS023 (Lactobacillus delbrueckii subsp. Bulgaricus strain NDO4)、嗜热链球菌HS033 (Streptococcus thermophilus 3233)对耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus, MRSA)的抑菌机制。方法 以MRSA为研究对象, 探索乳酸菌粗提物对MRSA菌株的最小抑菌浓度(minimum inhibitory concentration, MIC)的影响、抗菌药物复合作用对细菌生长的影响、抽提物对MRSA生物被膜抑制和清除效果, 以及抽提物对MRSA细胞膜完整性的破坏作用等。结果 乳酸菌粗提物HS011、HS023、HS033对MRSA的MIC分别为5.75、5.00、6.00 mg/mL; 指示菌MRSA的生长过程受到粗提物明显抑制, 在6 h时HS011、HS023、HS033对MRSA的抑菌率分别为28.69%、69.20%和42.19%; 3株乳酸菌粗提物与四环素复合使用时对MRSA的抑菌效果增强, 抑菌直径分别提高了39.33%、32.00%、37.43%, 但与亚胺培南复合使用时, 其抑菌效果却减弱了; 3株乳酸菌粗提物在1 MIC时对MRSA生物被膜形成具有一定的抑制和清除效果, 对生物被膜形成的抑制率分别为27.30%、18.20%、17.57%, 对成熟被膜的清除率分别为42.10%、54.50%、45.50%; 通过测定指示菌的核酸泄漏量、胞外蛋白含量以及扫描电镜成像发现乳酸菌粗提物处理过的MRSA, 其细胞膜被破坏。结论 3株乳酸菌的粗提物通过破坏MRSA的细胞膜有效抑制MRSA的生长和生物被膜的形成, 本研究结果为乳酸菌的抑菌机制探究提供一定的基础数据。

Antibacterial mechanism of crude extracts of lactic acid bacteria isolated from traditional fermented food against methicillin-resistant Staphylococcus aureus

Objective To explore the antibacterial mechanism of Lactobacillus plantarum MG5276 (HS011), Lactobacillus delbrueckii subsp. Bulgaricus strain NDO4 (HS023), and Streptococcus thermophilus 3233 (HS033) against methicillin-resistant Staphylococcus aureus (MRSA). Methods Taking MRSA as the research object, the effects of the crude extract of lactic acid bacteria on the minimal inhibitory concentration (MIC) of MRSA strain, the effects of antibacterial compound on bacterial growth, the inhibitory and scavenging effects of the extract on MRSA biofilm, and the destruction of the integrity of MRSA cell membrane by the extract were explored. Results The MIC value of lactic acid bacteria HS011, HS023 and HS033 crude extracts on MRSA was 5.75, 5.00 and 6.00 mg/mL, respectively. The growth of indicator bacteria MRSA was significantly inhibited by the crude extracts, and the antibacterial rates of HS011, HS023, and HS033 against MRSA at 6 h were 28.69%, 69.20%, and 42.19%, respectively. The antibacterial effects on MRSA were enhanced when crude extracts of 3 strains of lactic acid bacteria combined with tetracycline, with the antibacterial diameter increased by 39.33%, 32.00% and 37.43%, respectively; while used in combination with imipenem, its antibacterial effect was weakened. The crude extracts of three lactic acid bacteria had a certain inhibition and clearance effects on the MRSA biofilm formation at 1 MIC, with the inhibition rates 27.30%, 18.20% and 17.57%; and the clearance rates 42.10%, 54.50% and 45.50%, respectively. By measuring the nucleic acid leakage and extracellular protein content of the indicator bacteria MRSA, and by the image with scanning electron microscopy, it was found that the crude extracts of lactic acid bacteria had a good destructive effect on the MRSA cell membrane. Conclusion The crude extracts of 3 lactic acid bacteria can effectively inhibit the growth of MRSA and the formation of biofilm by destroying the cell membrane of MRSA. The results of this study provide certain basic data for the investigation of the antibacterial mechanism of lactic acid bacteria.