Iluz Natanel, Maor Yasmin, Keller Natan, Malik Zvi
The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
Laboratory of Clinical Microbiology, Sheba Medical Center, Ramat-Gan, Israel.
Lasers Surg Med. 2018 Jul;50(5):535-551. doi: 10.1002/lsm.22785. Epub 2018 Jan 15.
Staphylococcus aureus is a major pathogen in clinical microbiology. It is known to cause infections at various body sites and can be life-threatening. The development of resistance to many well-established antibiotic treatments and the prevalence of methicillin-resistant S. aureus (MRAS) among hospital patients and the general community pose challenges in treating the pathogen. The antimicrobial effect of photodynamic therapy (PDT) has been a subject of study for a long time and can offer new strategies for dealing with resistant strains.
In our study, we searched for a positive synergistic relationship between PDT and the standard antibiotics used to treat S. aureus and MRSA infections.
The phototoxic profile of deuteroporphyrin (DP) in both resistant and susceptible clinical strains of S. aureus was determined by plating of treated and untreated broth cultures. Electron microscopy imaging was done to explore possible sites of damage and free-radical accumulation in the cells during DP-PDT. Minimal inhibitory concentration (MIC) of oxacillin, gentamicin, vancomycin, rifampin, and fusidic acid was determined using the broth dilution method, and the checkerboard method was used to detect and evaluate the synergistic potential of DP-PDT and antibiotic combinations. A synergistic combination was further characterized using broth cultures and plating.
DP-PDT using a light dose of 15 J/cm showed a bactericidal effect even with a small concentration of 17 μM DP. Transmission electron microscopy indicated profound damage in the cell wall and cell membrane, and the appearance of mesosome-like structures. Free radicals tend to localize in the cell membrane and inside the mesosome. No synergistic effect was detected by combining PDT with gentamicin, vancomycin, rifampin, and fusidic acid treatments. A positive synergistic effect was observed only in DP-PDT-oxacillin combined treatment using the checkerboard method. The effect was observed in clinical antibiotic-resistant isolates after DP-PDT using a light dose of 46 J/cm and small concentrations of DP. Oxacillin MIC decreased below 2 μg/ml in resistant strains under such conditions. Cultures which did not undergo new cycles of DP-PDT recovered their original oxacillin resistance after a few generations.
PDT with porphyrins shows possible new therapeutic options in treating drug-resistant S. aureus at body sites suitable for irradiation. The synergistic effect of DP-PDT with oxacillin on clinical strains illustrates the potential of PDT to augment traditional antibiotic treatment based on cell wall inhibitors. Lasers Surg. Med. 50:535-551, 2018. © 2018 Wiley Periodicals, Inc.
金黄色葡萄球菌是临床微生物学中的主要病原体。已知它可在身体各个部位引起感染，并且可能危及生命。对许多成熟抗生素治疗产生耐药性以及医院患者和普通人群中耐甲氧西林金黄色葡萄球菌（MRAS）的流行，给该病原体的治疗带来了挑战。光动力疗法（PDT）的抗菌作用长期以来一直是研究的课题，可为应对耐药菌株提供新策略。
在我们的研究中，我们寻找PDT与用于治疗金黄色葡萄球菌和耐甲氧西林金黄色葡萄球菌（MRSA）感染的标准抗生素之间的正协同关系。
通过对处理和未处理的肉汤培养物进行平板接种，确定了氘代卟啉（DP）在金黄色葡萄球菌耐药和敏感临床菌株中的光毒性特征。进行电子显微镜成像以探索DP-PDT过程中细胞内可能的损伤部位和自由基积累情况。使用肉汤稀释法测定苯唑西林、庆大霉素、万古霉素、利福平及夫西地酸的最低抑菌浓度（MIC），并采用棋盘法检测和评估DP-PDT与抗生素组合的协同潜力。使用肉汤培养和平板接种对协同组合进行进一步表征。
即使使用低至17μM的DP浓度，光剂量为15 J/cm²的DP-PDT也显示出杀菌作用。透射电子显微镜显示细胞壁和细胞膜有严重损伤，并且出现了类似中间体的结构。自由基倾向于定位于细胞膜和中间体内部。将PDT与庆大霉素、万古霉素、利福平及夫西地酸治疗联合使用未检测到协同作用。仅在使用棋盘法的DP-PDT-苯唑西林联合治疗中观察到正协同作用。在使用光剂量为46 J/cm²和低浓度DP的DP-PDT后，在临床抗生素耐药分离株中观察到了这种效果。在这种条件下，耐药菌株中的苯唑西林MIC降至2μg/ml以下。未进行新的DP-PDT循环的培养物在几代后恢复了其原始的苯唑西林耐药性。
卟啉光动力疗法在适合照射的身体部位治疗耐药金黄色葡萄球菌方面显示出可能的新治疗选择。DP-PDT与苯唑西林对临床菌株的协同作用说明了光动力疗法增强基于细胞壁抑制剂的传统抗生素治疗的潜力。《激光外科与医学》50:535 - 551, 2018。© 2018威利期刊公司。
