Cernáková Lucia, Dižová Stanislava, Bujdáková Helena
Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Mlynská dolina, Ilkovicova 6, 842 15 Bratislava, Slovakia.
Med Mycol. 2017 Oct 1;55(7):748-753. doi: 10.1093/mmy/myw137.
A promising approach for the eradication of biofilm formed by the yeast Candida albicans seems to be photodynamic inactivation (PDI). This work presents a use of methylene blue (MB, 1 mM) irradiated with a red laser (output power 190 mW/cm2, wavelength 660 nm) for the eradication of a biofilm formed by the fluconazole-resistant (FLC-resistant) strain C. albicans CY 1123 compared to the standard strain C. albicans SC5314. The periods of irradiation corresponded to the fluence of 15, 23 and 57 J/cm2. Effectiveness of PDI was evident with following percentage of survived biofilm cells: 24.57, 23.46, and 22.29% for SC5314 and 40.28, 17.91, and 5.89% for CY 1123, respectively, compared to the samples without irradiation. Light and confocal laser scanning microscopy confirmed the effectiveness of PDI. However, the morphological form of C. albicans seems to play an important role as well, since prolonged duration of irradiation did not increase efficiency of PDI on C. albicans SC5314. An experiment with the yeast-to-hyphae transition revealed that the FLC-resistant strain expressed a markedly reduced capacity to form hyphae compared to SC5314. We summarized that PDI was effective on biofilm formed by the FLC-resistant strain, but resistance most likely did not play significant role in PDI. Additionally, we observed differences in susceptibility to PDI between biofilms composed of the mycelia and only of the yeasts, and finally, the employment of a laser in PDI enabled a decreasing period of irradiation while maintaining the high effectiveness of PDI.
光动力灭活（PDI）似乎是一种根除白色念珠菌形成的生物膜的有效方法。这项工作展示了使用亚甲蓝（MB，1 mM）并用红色激光（输出功率190 mW/cm²，波长660 nm）照射，以根除耐氟康唑（FLC耐药）菌株白色念珠菌CY 1123形成的生物膜，并与标准菌株白色念珠菌SC5314进行比较。照射时间对应于15、23和57 J/cm²的能量密度。PDI的有效性在存活的生物膜细胞百分比中很明显：与未照射的样品相比，SC5314分别为24.57%、23.46%和22.29%，CY 1123分别为40.28%、17.91%和5.89%。光学和共聚焦激光扫描显微镜证实了PDI的有效性。然而，白色念珠菌的形态形式似乎也起着重要作用，因为延长照射时间并没有提高PDI对白色念珠菌SC5314的效率。一项关于酵母向菌丝转变的实验表明，与SC5314相比，FLC耐药菌株形成菌丝的能力明显降低。我们总结认为，PDI对FLC耐药菌株形成的生物膜有效，但耐药性在PDI中很可能没有起到显著作用。此外，我们观察到由菌丝体和仅由酵母组成的生物膜对PDI的敏感性存在差异，最后，在PDI中使用激光能够在保持PDI高效性的同时缩短照射时间。
