Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran.
Photodiagnosis Photodyn Ther. 2012 Mar;9(1):11-5. doi: 10.1016/j.pdpdt.2011.11.004. Epub 2011 Dec 16.
Photodynamic inactivation (PDI) has been investigated to cope with the increasing incidence of multidrug-resistant (MDR) pathogens. Here we studied the PDI mediated by methylene blue (MB) and toluidine blue O (TBO) in clinical methicillin-resistant Staphylococcus aureus and MDR Escherichia coli, together with their corresponding American Type Culture Collection (ATCC) strains.
Effect of photosensitizer concentration (12.5, 25, 50 μg/ml) and laser irradiation time (10, 20 and 30 min) on lethal photosensitization was investigated.
TBO was more effective. TBO at 50 μg/ml, 46.8 J cm⁻², exhibited 0.7 log killing for MDR E. coli and 1.7 log killing for E. coli (ATCC 25922); 3.1 log killing for MRSA, and 4.2 log killing for S. aureus (ATCC 25923). MB at 50 μg/ml, 163.8 J cm⁻², only exhibited 2.2 log killing in MRSA and 3.1 log killing in S. aureus (ATCC 25923). MB (50 μg/ml, 163.8 J cm⁻²) induced 0.2 log killing for MDR E. coli and 0.3 log killing for E. coli (ATCC 25922). After TBO-PDI, MDR isolates were more susceptible to some antibiotics than control groups.
Our studied clinical isolates were more resistant to PDI-mediated killing than their ATCC reference strains. Thus, TBO/MB-mediated PDI in other MDR isolates deserves further investigation.
光动力灭活（PDI）已被研究用于应对日益增加的多药耐药（MDR）病原体。在这里，我们研究了亚甲蓝（MB）和甲苯胺蓝 O（TBO）介导的临床耐甲氧西林金黄色葡萄球菌和多药耐药大肠杆菌，以及它们相应的美国典型培养物保藏中心（ATCC）菌株的 PDI。
研究了光敏剂浓度（12.5、25、50μg/ml）和激光辐照时间（10、20 和 30 分钟）对致死光敏化的影响。
TBO 更有效。TBO 浓度为 50μg/ml、激光能量密度为 46.8 J/cm²，对多药耐药大肠杆菌的杀菌率为 0.7 log，对大肠杆菌（ATCC 25922）的杀菌率为 1.7 log；对耐甲氧西林金黄色葡萄球菌的杀菌率为 3.1 log，对金黄色葡萄球菌（ATCC 25923）的杀菌率为 4.2 log。MB 浓度为 50μg/ml、激光能量密度为 163.8 J/cm²，对耐甲氧西林金黄色葡萄球菌的杀菌率仅为 2.2 log，对金黄色葡萄球菌（ATCC 25923）的杀菌率为 3.1 log。MB（50μg/ml、163.8 J/cm²）诱导多药耐药大肠杆菌的杀菌率为 0.2 log，诱导大肠杆菌（ATCC 25922）的杀菌率为 0.3 log。TBO-PDI 后，与对照组相比，MDR 分离株对一些抗生素的敏感性更高。
我们研究的临床分离株对 PDI 介导的杀伤比其 ATCC 参考菌株更具抗性。因此，TBO/MB 介导的 PDI 在其他 MDR 分离株中值得进一步研究。
