碩士 / 國立臺灣大學 / 醫學檢驗暨生物技術學研究所 / 99 / Like the appearance of methicillin-resistant Staphylococcus aureus (MRSA), the developments of antibiotics-resistant events among a variety of bacteria are due to antibiotics abuses. Drug-resistant strains spring up like mushrooms that indicates antibiotics therapy not enough. To solve these problems, photodynamic inactivation is other anti-microbial strategies. Photodynamic inactivation employs visible light of appropriate wavelength to excite the photosensitizer and then the photosensitizer goes through a transition from ground state to triplet excited state. The triplet excited photosensitizer generates free radicals from electron transfer or reacts with oxygen molecules to produce singlet oxygen. Free radicals and singlet oxygen are toxic to bacteria because of destroying their components such as cell wall, cell membrane and nucleotides. Chitosan is from chitin undergoing deacetylation, and it exhibits antimicrobial effects. In this study, we investigated whether TBO combined with chitosan showed synergistic photodynamic inactivation.
The trends of increasing prevalence of MRSA infections worldwide indicate that there are more challenges of MRSA therapy. Biofilms are 100 to 1,000 times less susceptible to antibiotics than planktonic bacteria, so it is difficult to handle biofilm prevention. This study focused on Staphylococcus aureus; one was ATCC 29213 (methicillin-sensitive S. aureus), another was ATCC 33592 (MRSA), and the others were four clinical MRSA strains. The photosensitizer was chosen cationic toluidine blue O (TBO) and then we used red LED light to excite it for evaluating the synergistic photodynamic inactivation efficiency of TBO combined with chitosan against planktonic and biofilm cells. In addition, this study also explored the influence of protease activity under TBO combined with chitosan treatment.
The synergistic photodynamic inactivation for S. aureus planktonic cells could be detected under the conditions of low concentration of TBO; however, the effect for biofilm cells was only observed when TBO doses were increased. The synergistic photodynamic inactivation that was supposed to be associated with various genetic regulation and characteristics of bacterial stages affected biofilms less than planktonic cells. According to the results, there was no obvious difference of the synergistic photodynamic inactivation efficiency between methicillin-susceptible or resistant strains including diverse SCCmec types. Thus, the synergistic photodynamic activity by TBO combined with chitosan was shown in all of the tested S. aureus strains. Moreover, chitosan had the ability to inhibit protease activities of S. aureus.
| Identifer | oai:union.ndltd.org:TW/099NTU05108118 |
| Date | January 2011 |
| Creators | Hong-Sih Jiang, 江紅思 |
| Contributors | 鄧麗珍 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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