中文摘要

自從1990年初期以來，Acinetobacter 被視為醫院內重要的細菌之一。在Acinetobacter 物種之中，最常出現的一株為鮑式不動桿菌Acinetobacter baumannii(簡稱A. baumannii) 。此類物種為需氧的葛蘭氏陰性菌(Gram-)。A. baumannii通常會經由唾液、身體分泌物、尿液、腦脊液蛋白及腹膜液，造成肺炎、尿道感染和諸多的病症。此菌種每年造成台灣人民死亡率達60%之高。而大多數的抗生素對此鮑式不動桿菌都是沒有效用的，但Penicillin 及sulbactam這二種抗菌藥物卻對鮑式不動桿菌有抑制的反應。所以在此探討二種抗生素對於鮑式不動桿菌的反應機制。

抗生素藥物分子能附著在生物膜結構的表面，顯示在膜上的行為表現。在此篇研究中，使用penicillin及sulbactum作為標靶藥物與生物合成膜作用。本實驗先用合成生物膜代替鮑式不動桿菌，另外也使用文獻中已知的cholesterol來當作參考資料。藉此使用二種不同的實驗方法對這個主題作深入的探討。其一就是將脂質lipid以電生成的方法長成巨型單層微胞(GUVs) ，再使用螢光顯微鏡研究分析。巨型單層微胞對於藥物分子附著過程的動力學及造成面積改變的原因。第二就是在國家同步輻射研究中心，利用13A光束實驗站的多片層X光繞射技術(LXD) 。以此方法利用不同藥物分子及脂質的莫耳濃度比率來測量生物膜厚度的改變對於整個機制的影響。這二種實驗結果中，膽固醇cholesterol及二種抗生素藥物penicillin、sulbactum在動力學和片層繞射實驗對於生物膜有截然不同的結果。藉此實驗能延伸到活體外in vivo的應用，希望不久的將來能與醫學臨床有所結合直接應用於藥物設計上。

Abstract

Acinetobacter baumannii is a species of pathogenic bacterium, referred to as an aerobic gram-negative bacterium. Acinetobacter have been recognized as important nosocomial bacteria since 1990s. A. baumannii is often found in the sputum, body secretion, urine, and the cerebrospinal fluid or peritoneal fluid of the patients, including intubated patients in hospitals. It will lead to serious pneumonia, infections of the urinary tract and even fatal consequences. The bacterium results in 60% death rate of Taiwan hospital patients each year. Most antibiotics are ineffective against A. baumannii currently. Penicillin and sulbactam were used to study the mechanism of drug resistance presented by A. baumannii.

Antibiotic drug resistance is a serious issue for the treatment of bacterial infection. Understanding the resistance of antibiotics is a key issue for developing new drugs. In this study, we used penicillin and sulbactam as the model antibiotics to interact with model membranes. Cholesterol was used to target the membrane for comparison with the well-known insertion model. Lamellar X-ray diffraction (LXD) was used to determine membrane thickness using successive drug-to-lipid molar ratios. The aspiration method for a single giant unilamellar vesicle (GUV) was used to monitor the kinetic binding process of antibiotic-membrane interactions in an aqueous solution. Both penicillin and sulbactam are found lying outside the model membrane, and cholesterol inserts perpendicularly into the hydrophobic region of the membrane in aqueous solution. This result provides structural insights for understanding the antibiotic-membrane interaction and the mechanism of antibiotics.

Keywords: Acinetobacter baumannii, penicillin, sulbactam, cholesterol, GUV, LXD

Abbreviations: A. baumannii, Acinetobacter baumannii; LXD, Lamellar X-ray diffraction; GUV, giant unilamellar vesicle

Chapter 5
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