State Key Laboratory of Pathogen and Biosecurity, Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences, Beijing, China.
PLoS One. 2013 Jul 23;8(7):e67728. doi: 10.1371/journal.pone.0067728. Print 2013.
Streptococcus suis (S.suis) is an important emerging worldwide pig pathogen and zoonotic agent with rapid evolution of virulence and drug resistance. In this study, we wanted to investigate the effect of licochalcone A on growth and properties of Streptococcus suis. The antimicrobial activity of licochalcone A was tested by growth inhibition assay and the minimal inhibitory concentrations (MICs) also were determined. The effect of licochalcone A on S.suis biofilm formation was characterized by crystal violet staining. The effect of licochalcone A on suilysin secretion was evaluated by titration of hemolytic activity. To understand the antimicrobial effect, gene expression profile of S.suis treated by licochalcone A was analyzed by DNA microarray. Our results demonstrated that licochalcone A showed antimicrobial activity on S.suis with MICs of 4 µg/ml for S.suis serotype 2 strains and 8 µg/ml for S.suis serotype 7 strains. Biofilm formation was inhibited by 30-40% in the presence of licochalcone A (3 µg/ml) and suilysin secretion was also significantly inhibited in the presence of licochalcone A (1.5 µg/ml). The gene expression profile of S.suis in the presence of licochalcone A showed that 132 genes were differentially regulated, and we analyzed the regulated genes in the aspect of the bacterial cell cycle control. Among the deregulated genes, the genes responsible for the mass doubling was increased expression, but the genes responsible for DNA replication and cell division were inhibited the expression. So, we think the regulation of the cell cycle genes might provide a mechanistic understanding of licochalcone A mediated antimicrobial effect against S.suis.
猪链球菌（S.suis）是一种重要的新兴的全球猪病原体和人畜共患病病原体，其毒力和耐药性迅速进化。在本研究中，我们研究了甘草查尔酮 A 对猪链球菌生长和特性的影响。通过生长抑制试验测试了甘草查尔酮 A 的抗菌活性，并确定了最小抑菌浓度（MICs）。通过结晶紫染色法表征了甘草查尔酮 A 对猪链球菌生物膜形成的影响。通过测定溶血活性评估了甘草查尔酮 A 对苏利菌素分泌的影响。为了了解抗菌作用，通过 DNA 微阵列分析了甘草查尔酮 A 处理的猪链球菌基因表达谱。结果表明，甘草查尔酮 A 对猪链球菌具有抗菌活性，猪链球菌血清型 2 株的 MICs 为 4 µg/ml，猪链球菌血清型 7 株的 MICs 为 8 µg/ml。在 3 µg/ml 甘草查尔酮 A 的存在下，生物膜形成抑制了 30-40%，在 1.5 µg/ml 甘草查尔酮 A 的存在下，苏利菌素分泌也显著受到抑制。甘草查尔酮 A 存在下的猪链球菌基因表达谱显示，有 132 个基因差异调控，我们从细菌细胞周期控制的角度分析了调控基因。在失调基因中，负责倍增的基因表达增加，但负责 DNA 复制和细胞分裂的基因表达受到抑制。因此，我们认为细胞周期基因的调节可能为甘草查尔酮 A 介导的抗猪链球菌抗菌作用提供了机制理解。
