Microbial drug-resistance demands immediate implementation of novel therapeutic strategies. Antimicrobial photodynamic therapy (aPDT) combines the administration of a photosensitizer (PS) compound with low-irradiance light to induce photochemical reactions that yield reactive oxygen species (ROS). Since ROS react with nearly all biomolecules, aPDT offers a powerful multitarget method to avoid selection of drug-resistant strains. In this study, we assayed photodynamic inactivation under a standardized method, combining methylene blue (MB) as PS and red light, against global priority pathogens. The species tested include Acinetobacter baumannii, Klebsiella aerogenes, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecium, Enterococcus faecalis, Staphylococcus aureus, Candida albicans and Cryptococcus neoformans. Our strain collection presents resistance to all tested antimicrobials (>50). All drug-resistant strains were compared to their drug-sensitive counterparts. Regardless of resistance phenotype, MB-aPDT presented species-specific dose-response kinetics. More than 5log10 reduction was observed within less than 75 s of illumination for A. baumannii, E. coli, E. faecium, E. faecalis and S. aureus and within less than 7 min for K. aerogenes, K. pneumoniae, P. aeruginosa, C. albicans and C. neoformans. No signs of correlations in between drug-resistance profiles and aPDT sensitivity were observed. Therefore, MB-aPDT can provide effective therapeutic protocols for a very broad spectrum of pathogens. Hence, we believe that this study represents a very important step to bring aPDT closer to implementation into mainstream medical practices.

中文翻译：

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全球优先的耐多药病原体不能抵抗光动力疗法。

微生物耐药性要求立即实施新的治疗策略。抗菌光动力疗法（aPDT）将光敏剂（PS）化合物与低辐射光结合使用，以引发产生活性氧（ROS）的光化学反应。由于ROS与几乎所有生物分子发生反应，因此aPDT提供了一种强大的多目标方法，可避免选择耐药菌株。在这项研究中，我们分析了针对全局优先病原体的标准化方法下的光动力学失活，将亚甲基蓝（MB）作为PS和红光相结合。被测试的物种包括鲍曼不动杆菌，产气克雷伯菌，大肠杆菌，肺炎克雷伯菌，铜绿假单胞菌，粪肠球菌，粪肠球菌，金黄色葡萄球菌，白色念珠菌和新隐球菌。我们的菌株收集物表现出对所有经过测试的抗生素的抵抗力（> 50）。将所有耐药菌株与其对药物敏感的菌株进行比较。不管抗性表型如何，MB-aPDT都呈现出物种特异性的剂量反应动力学。对于鲍曼不动杆菌，大肠杆菌，粪肠球菌，粪肠球菌和金黄色葡萄球菌，在少于75秒的光照下观察到超过5log10的减少；对于产气链球菌，肺炎克雷伯氏菌，在少于7分钟的时间内观察到减少。铜绿，白色念珠菌和新孢子虫。在耐药性谱图和aPDT敏感性之间未发现相关的迹象。因此，MB-aPDT可以为多种病原体提供有效的治疗方案。因此，我们相信这项研究代表了非常重要的一步，可以使aPDT更加接近主流医疗实践。