細菌利用發酵的干擾作用發生在自然界。例如微生物在腐爛中的水果可轉換澱粉成醣類。這些微生物以醣類為碳源利用發酵產生短鏈脂肪酸(SCFAs)抵抗其他微生物的入侵。這也是一種演化機 制，微生物利用發酵作用來抵抗同營養源的競爭者。糖尿病傷口感染是一種在低氧環境並包含多種微生物在傷口滋長。我們認為微生物在糖尿病傷口互相競爭如同腐爛水果內微生物間的干擾作 用。我們假設皮膚共生菌與金黃葡萄球菌(S. aureus)共同存在糖尿病傷口，並彼此利用發酵作用互相抵抗。我們將從共生菌的發酵產物中發展一種可以清除金黃色葡萄球菌的藥物(Co-drug)。本研究計畫將利用第二型糖尿病老鼠形成皮膚傷口並感染金黃葡萄球菌。 我們提出三個目標來測試我們的假設： 目標一：我們定量SCFA 在傷口的濃度，決定是否甘油發酵是否對於殺死金黃葡萄球菌是必需的，並獲得有效的SCFA 可殺死各種不同金黃葡萄球菌株。 目標二：我們將合成一個帶有兩個活性的SCFA 的Co-drug，確定皮膚共生菌在傷口內與金黃葡萄球菌的干擾作用，並決定Co-drug 的藥效。 目標三：我們將鑑定SCFA 處理的糖尿病傷口內產生細胞因子(Cytokine)的變化，探討SCFAs對細菌感染的免疫調節(Immunomodulatory)的作用，並利用Ffar1 突變老鼠調查脂肪酸感受體對於SCFA 免疫調節作用的必要性。 我們在此定義皮膚共生菌是一種益生菌，並可利用發酵作用來清除金黃葡萄球菌。發酵產物中的SCFAs 及其衍生物可發展有效的抗金黃葡萄球菌藥物，以提供一種清除金黃葡萄球菌在糖尿病傷 口感染的治療模式。 ;Bacterial interference via fermentation occurs in natural ecosystems. For example, fruit ripening involves the conversion of starch to carbohydrates. Microorganisms widespread both on and inside fruits consume carbohydrates as carbon sources to initiate the fermentation and produce short-chain fatty acids (SCFAs). Ferments produced by fermentative microorganisms appear to have specifically evolved to inhibit the activity of bacterial competitors within the ripe fruit. Fermentation of microorganisms in ripens fruits may, in fact, be part of an evolved strategy to compete with other microbes for access to nutrients. As tissue hypoxia (oxygen-limited) with a polymicrobial nature is one of the pathophysiological characteristics of infections in diabetic ulcers, we imagine that bacterial antagonism in a microenvironment of diabetic ulcers may be similar to bacterial interference a ripening fruit. Staphylococcus aureus (S. aureus) bacteria are the predominant pathogens in infections of diabetic ulcers. We hypothesize that skin commensal bacteria and S. aureus co-exist within an oxygen-limited diabetic ulcer and that bacteria within a diabetic ulcer exploit fermentation to edge each other out for maximum survival. A novel co-drug derived from SCFAs, major fermentation productions of skin commensal bacteria, will be designed to ward off S. aureus. Type-2 diabetic Lepr(db/db) mice will be used as a diabetic model to study the S. aureus wound infection. Three Specific Aims are proposed to test our hypothesis. In Specific Aim 1, we will measure the concentrations of SCFAs in a wounded skin, determine the essential role of glycerol fermentation of commensal bacteria in the eradication of S. aureus skin colonization, and obtain SCFAs with broad-spectrum anti-S. aureus activities. In Specific Aim 2, we will synthesize the SCFA co-drugs that carry two active SCFAs, confirm the interference of commensal bacteria via glycerol fermentation with S. aureus in diabetic ulcers, and evaluate the treatments of SCFA co-drugs for the abolition of S. aureus carriage in diabetic ulcers. In Specific Aim 3, we will identify the cytokine profiles in SCFA-treated diabetic wounds, explore the immunomodulatory effects of SCFAs on bacterial colonization, and investigate the essential role of free fatty acid receptor 1 (Ffar 1) in the action of SCFAs. Skin commensal bacteria, which we define as probiotic bacteria in this proposal,mediate glycerol fermentation as an evolved strategy to outcompete S. aureus. The derivatives of SCFAs produced by fermenting commensal bacteria as antimicrobial agents provide a new set of tools for fighting S. aureus infection in diabetic wounds.
