氨基酮戊酸光动力对表皮葡萄球菌生物膜作用

目的 探讨氨基酮戊酸光动力（ALA-PDT）对表皮葡萄球菌生物膜的作用。方法 盖玻片上培养并形成表皮葡萄球菌生物膜，激光共聚焦显微镜（CLSM）观察其结构；将实验分为不同光剂量（100 ~ 300 J/cm2）的ALA-PDT组和阴性对照组及单纯红光照射组。采用活菌计数法评估ALA-PDT对生物膜细菌的杀菌作用，CLSM观察ALA-PDT对生物膜细菌活力的影响，扫描电镜检测ALA-PDT对生物膜结构的影响。结果 ＡＬＡ－ＰＤＴ组分别给予100、200、300 J/cm2红光照射后，存活的细菌数分别为（210 ± 7.55） × 105、（91 ± 1.53） × 105、（16 ± 1.52） × 105，经统计学分析，各组和阴性对照组及单纯红光照射组之间，差异均有统计学意义（P < 0.01）；死菌/活菌比例分别为1.254 ± 0.096、1.301 ± 0.160、3.410 ± 1.140，各组与阴性对照组及单纯红光照射组之间差异有统计学意义（P < 0.01）。扫描电镜结果显示，生物膜结构疏松、模糊，当光剂量达300 J/cm2时，生物膜结构消失，细菌呈单菌落分布。结论 ALA-PDT对生物膜有一定的抗菌作用，不仅能降低生物膜的活力，还能破坏生物膜的结构。

Effects of 5-aminolevulinic acid-based photodynamic therapy on Staphylococcus epidermidis biofilms

Objective To evaluate the effect of 5-aminolevulinic acid-based photodynamic therapy （ALA-PDT） on S. epidermidis biofilms. Methods S. epidermidis was cultured on cover glasses, with or without the presence of ALA at 50 mmol/L for 16 hours followed by the exposure to different doses （100, 200, 300 J/cm2） of red light. S. epidermidis receiving neither pretreatment nor irradiation served as the negative control. Subsequently, confocal laser scanning microscopy （CLSM） was used to observe the structure and evaluate the biological activity of S. epidermidis biofilms; colony forming units （CFUs） of S. epidermidis were counted for the evaluation of killing effect of ALA-PDT; scanning electron microscopy （SEM） was used to observe the morphological structure of the biofilms. Results The number of colony forming units per milliliter （CFU/ml） was （210 ± 7.55） × 105, （91 ± 1.53） × 105, （16 ± 1.52） × 105 for S. epidermidis pretreated with ALA followed by irradiation with red light at 100, 200 and 300 J/cm2 respectively, significantly different from untreated S. epidermidis （（388 ± 8.89） × 105, all P < 0.01） and S. epidermidis irradiated with red light only. Increased ratio of dead to live cells was observed in ALA-pretreated S. epidermidis irradiated with red light at 100, 200 and 300 J/cm2 compared with untreated S. epidermidis （1.254 ± 0.096, 1.301 ± 0.160 and 3.410 ± 1.140 vs. 0.358 ± 0.057, all P < 0.01） and S. epidermidis irradiated with red light only. SEM showed that the biofilm structure was loose and obscure in S. epidermidis treated with ALA-PDT, and even disappeared with S. epidermidis distributed in single colonies when the dose of red light was 300 mJ/cm2. Conclusion ALA-PDT shows a potential bactericidal activity against S. epidermidis in biofilms, which can not only reduce biofilm vitality, but also damage biofilm structure.