芦荟苷对金黄色葡萄球菌生长抑制作用及对溶血毒素表达的影响

Inhibitory effects of aloin on growth activity and hemolytic toxin expression of Staphylococcus aureus

目的研究芦荟苷体外对金黄色葡萄球菌生长抑制作用以及对溶血素表达的影响。方法采用肉汤倍比稀释法检测芦荟苷水溶物对金黄色葡萄球菌最低抑菌浓度(MIC);琼脂打孔法观察芦荟苷对金黄色葡萄球菌的抑菌圈大小;试管法检测芦荟苷作用下金黄色葡萄球菌凝固酶的产生变化;检测芦荟苷作用下金黄色葡萄球菌溶血素活性变化;采用实时荧光定量PCR检测芦荟苷水溶物作用于金黄色葡萄球菌后对hla和agr A基因表达的影响。结果芦荟苷水溶物可抑制金黄色葡萄球菌生长并呈现浓度依赖性,作用于ATCC 25923和临床菌株SA1.5后的抑菌圈直径和MIC分别为21.5 mm、12.5 mg/m L和17mm、15 mg/m L;与对照组凝固酶效价32比较,1/2MIC组、MIC和2MIC组芦荟苷作用ATCC 25923后的凝固酶效价分别降为16、4和2;与对照组相比,1/2MIC组、MIC组及2MIC组芦荟苷水溶物降低ATCC 25923溶血活性,溶血率分别为(77.4±3.41)%、(42.2±2.4)%和(38.7±2.4)%;1/2MIC组、MIC组和2MIC组芦荟苷作用ATCC 25923后hla表达量分别为0.020 3(0.019 6,0.028 8)、0.011 6(0.010 6,0.013 1)和0.033 7(0.020 2,0.042 9),3组间差异有统计学意义(H=16.807,P<0.05);agr A表达量分别为0.074 6(0.066 2,0.098 2)、0.020 8(0.012 2,0.032 6)和0.021 3(0.010 2,0.029 6),3组间差异有统计学意义(H=16.320,P<0.05)。结论芦荟苷可抑制金黄色葡萄球菌生长,并对α-溶血素表达有抑制作用。

Objective To investigate the inhibitory effects of aloin on the growth of Staphylococcus aureus and its virulence factors ahemolysin in vitro. Methods Broth dilution was used to measure the minimum inhibitory concentration （MIC） of water-soluble aloin on S. aureus. Agar drilling method was used to observe the size of inhibition zone of aloin for S. aureus. Plasma coagulase test was used to detect the changes of S. aureus coagulase and absorbance was measured to detect the changes of hemolytic activity when S. au-reus was exposed to aloin. Real time PCR was used to detect the effects of aloin on the expressions of hla and agrA mRNA. Results The soluble aloin inhibited the growth of S. aureus in a dose-dependent manner. The inhibition zone diameter of a standard strain of S. aureus (ATCC 25923) was 21.5 mm with MIC of 12.5 mg/mL and 17 mm for the clinical isolate SA1.5 with MIC of 15 mg/mL. After treated with soluble aloin, the eoagulase titers of ATCC 25923 were 16, 4 and 2 for 1/2 MIC, 1 MIC and 2 MIC respectively compared with titer 32 of the control group without soluble aloin. The expression of a-hemolysin of S. aureus ATCC 25923 was downregulated by soluble aloin and the hemolytic activity of S. aureus ATCC 25923 with 1/2 MIC, 1 MIC and 2 MIC groups were （77.4 ± 3.41) %, （42.2 ± 2.4） % and （38.7 ± 2.4） % respectively. The expression levels of hla were 0. 020 3 （0. 019 6, 0. 028 8）, 0.011 6（0.010 6, 0.013 1） and 0.033 7（0.020 2, 0.042 9） respectively in the 1/2 MIC, 1 MIC and 2 MIC group respectively, and there were significant differences among the three groups (H = 16. 807, P 〈 0.05). The expression levels of agrA was 0. 074 6 （0.066 2, 0.098 2）, 0.020 8 （0.012 2, 0.032 6） and 0.021 3 （0.010 2, 0.029 6） in the 1/2 MIC, 1 MIC and 2 MIC group respectively, and there were significant differences among the three groups （H = 16. 320, P 〈 0.05). Conclusion Aloin may inhibit the growth of S. aureus and could effectively inhibit the expression of a-hemolysin.