Omar Ghada S, Wilson Michael, Nair Sean P
Division of Microbial Diseases, UCL Eastman Dental Institute, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
BMC Microbiol. 2008 Jul 1;8:111. doi: 10.1186/1471-2180-8-111.
The increase in resistance to antibiotics among disease-causing bacteria necessitates the development of alternative antimicrobial approaches such as the use of light-activated antimicrobial agents (LAAAs). Light of an appropriate wavelength activates the LAAA to produce cytotoxic species which can then cause bacterial cell death via loss of membrane integrity, lipid peroxidation, the inactivation of essential enzymes, and/or exertion of mutagenic effects due to DNA modification. In this study, the effect of the LAAA indocyanine green excited with high or low intensity light (808 nm) from a near-infrared laser (NIR) on the viability of Staphylococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa was investigated.
All species were susceptible to killing by the LAAA, the bactericidal effect being dependent on both the concentration of indocyanine green and the light dose. Indocyanine green photosensitization using both high (1.37 W cm(-2)) and low (0.048 W cm(-2)) intensity NIR laser light was able to achieve reductions of 5.6 log10 (>99.99%) and 6.8 log10 (>99.99%) in the viable counts of Staph. aureus and Strep. pyogenes (using starting concentrations of 106-107 CFU ml(-1)). Kills of 99.99% were obtained for P. aeruginosa (initial concentration 108-109 CFU ml(-1)) photosensitized by the high intensity light (1.37 W cm(-2)); while a kill of 80% was achieved using low intensity irradiation (0.07 W cm(-2)). The effects of L-tryptophan (a singlet oxygen scavenger) and deuterium oxide (as an enhancer of the life span of singlet oxygen) on the survival of Staph. aureus was also studied. L-tryptophan reduced the proportion of Staph. aureus killed; whereas deuterium oxide increased the proportion killed suggesting that singlet oxygen was involved in the killing of the bacteria.
These findings imply that indocyanine green in combination with light from a near-infrared laser may be an effective means of eradicating bacteria from wounds and burns.
致病细菌对抗生素的耐药性增加，因此需要开发替代抗菌方法，如使用光激活抗菌剂（LAAA）。适当波长的光激活LAAA产生细胞毒性物质，这些物质可通过膜完整性丧失、脂质过氧化、必需酶失活和/或由于DNA修饰产生诱变效应导致细菌细胞死亡。在本研究中，研究了近红外激光（NIR）发出的高或低强度光（808nm）激发的LAAA吲哚菁绿对金黄色葡萄球菌、化脓性链球菌和铜绿假单胞菌活力的影响。
所有菌种均对LAAA杀菌敏感，杀菌效果取决于吲哚菁绿浓度和光剂量。使用高（1.37W cm(-2)）和低（0.048W cm(-2)）强度的近红外激光进行吲哚菁绿光致敏，能够使金黄色葡萄球菌和化脓性链球菌的活菌数分别降低5.6 log10（>99.99%）和6.8 log10（>99.99%）（起始浓度为106 - 107 CFU ml(-1)）。高强度光（1.37W cm(-2)）致敏的铜绿假单胞菌（初始浓度108 - 109 CFU ml(-1)）杀菌率达99.99%；低强度照射（0.07W cm(-2)）杀菌率达80%。还研究了L - 色氨酸（单线态氧清除剂）和氧化氘（作为单线态氧寿命增强剂）对金黄色葡萄球菌存活的影响。L - 色氨酸降低了被杀死的金黄色葡萄球菌比例；而氧化氘增加了被杀死的比例，表明单线态氧参与了细菌的杀灭。
这些发现表明，吲哚菁绿与近红外激光结合可能是从伤口和烧伤中根除细菌的有效手段。
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