Institute of Medical Microbiology and Hygiene, Saarland University, Germany.
Department of Physics, University of Kaiserslautern, Germany.
J Photochem Photobiol B. 2016 Sep;162:340-347. doi: 10.1016/j.jphotobiol.2016.07.007. Epub 2016 Jul 9.
Multidrug-resistant Staphylococcus aureus (MDR-SA) are a frequent cause of antibiotic treatment refractory bacterial corneal infections. Photodynamic therapy (PDT) is being discussed as a putative treatment option to cure this type of bacterial infection. Here we tested the in vitro susceptibility of a set of 12 clinically derived MDR-SA isolates with differing genetic backgrounds and antibiotic resistance profiles against photodynamic inactivation (PDI) by the porphyrin chlorin e6 (Ce6) and red light (λ=670nm). All tested clinical isolates displayed a 5-log10 reduction in viable cells by Ce6 and red light, when cells were preincubated with the photosensitizer at concentrations ≥128μM for 30min in the dark, and a subsequent irradiation with light at λ=670nm (power density: 31mW/cm(2), absorbed dose: 18,6J/cm(2)) was applied. Similarly, cells of the laboratory strain Newman required the same Ce6 pre-incubation and light dose for a 5-log10 reduction in cell viability. Inactivation of crtM in strain Newman, which interferes with pigment production in S. aureus, rendered the mutant more susceptible to this PDT procedure, indicating that the level of resistance of S. aureus to this therapy form is affected by ability of the pathogen to produce the carotenoid pigment staphyloxanthin. Incubation of freshly explanted porcine corneas with a 0.5% Ce6 gel demonstrated that the photosensitizer can diffuse into and accumulate within the stroma of the cornea in concentrations found to be sufficient to yield a 5-log10 reduction of the S. aureus cell pool in vitro. These data suggest that PDI with Ce6 and red light might be a promising new option for the treatment of MDR-SA induced corneal infections.
耐多药金黄色葡萄球菌（MDR-SA）是抗生素治疗无效的细菌性角膜感染的常见原因。光动力疗法（PDT）被认为是治疗这种类型细菌感染的一种可能的治疗选择。在这里，我们测试了一组 12 种具有不同遗传背景和抗生素耐药谱的临床分离的 MDR-SA 对光敏剂原卟啉氯己酮（Ce6）和红光（λ=670nm）的光动力失活（PDI）的体外敏感性。当细胞在黑暗中用浓度≥128μM 的光敏剂预孵育 30min 后，并用 λ=670nm 的光（功率密度：31mW/cm(2)，吸收剂量：18.6J/cm(2)）进行后续照射时，所有测试的临床分离物的活细胞数量均减少了 5 个对数。同样，实验室菌株 Newman 的细胞也需要相同的 Ce6 预孵育和光剂量才能减少 5 个对数的细胞活力。在 Newman 菌株中敲除 crtM 会干扰金黄色葡萄球菌中色素的产生，从而使突变体对这种 PDT 程序更敏感，这表明金黄色葡萄球菌对这种治疗形式的耐药程度受到病原体产生类胡萝卜素色素番茄红素的能力的影响。将 0.5%Ce6 凝胶孵育新鲜取出的猪眼角膜表明，光敏剂可以扩散到角膜基质中并积累到足以使体外金黄色葡萄球菌细胞池减少 5 个对数的浓度。这些数据表明，Ce6 和红光的 PDI 可能是治疗 MDR-SA 诱导的角膜感染的一种有前途的新选择。
