【摘要】：腸出血性大腸桿菌O157∶H7作為新發(fā)傳染病病原菌可以導(dǎo)致出血性腸炎(hemorrhagic colitis，HC)和腎溶血性尿毒綜合癥(hemolytic uremic syndrome，HUS)，嚴(yán)重危害人類的身體健康�？股匾话悴荒苡糜谂R床治療大腸桿菌O157∶H7的感染性疾病。原因在于：傳統(tǒng)的治療過程中所使用的抗生素是基于以與細(xì)菌細(xì)胞的生長分裂有密切關(guān)系的系統(tǒng)為靶位點(diǎn)所分離得到的化合物。因?yàn)樵擃惢衔锏暮Y選原則是殺死或抑制細(xì)菌細(xì)胞的生長，因此會造成細(xì)菌細(xì)胞的SOS系統(tǒng)激活，進(jìn)而導(dǎo)致O157∶H7基因組中溶原型噬菌體933v和933w分別編碼的志賀毒素Stx1和Stx2的短期大量表達(dá)，從而加速宿主的死亡。所以，篩選不誘導(dǎo)志賀毒素表達(dá)的藥物和／或益生菌，以預(yù)防和控制大腸桿菌O157∶H7等病原菌感染引發(fā)的疾病，在理論和臨床疾病預(yù)防控制上都有重要意義。本文擬研究利用芽孢菌類益生菌控制大腸桿菌O157∶H7感染的可行性。 細(xì)菌細(xì)胞間通訊系統(tǒng)，即群體感應(yīng)(quorum sensing，QS)系統(tǒng)在協(xié)調(diào)病原菌在感染宿主的過程中各項(xiàng)生理活動中發(fā)揮著舉足輕重的作用，該系統(tǒng)通過自身產(chǎn)生一類稱為自誘導(dǎo)物質(zhì)(autoinducer，AI)的化學(xué)信號分子協(xié)調(diào)細(xì)菌整個群體的生理活動，許多病原菌的毒素釋放就受QS系統(tǒng)的調(diào)控。因此，以大腸桿菌O157∶H7等病原菌的QS系統(tǒng)為靶位點(diǎn)所篩選得到的抗菌藥物(antibacterials)，有可能不直接殺死細(xì)菌，而僅僅只是阻斷或干擾群體中個體之間的交流、進(jìn)而阻止它們釋放毒素，成為目前國際上藥物篩選的最新空間。 腸道益生菌是治療O157∶H7等腸道病原微生物感染的另一途徑，，比起抗生素有其優(yōu)勢的方面，其中就包括不會造成抗藥性的產(chǎn)生。而且本文所研究的H24菌株是對雞、豬、牛等動物腹瀉具有普遍的預(yù)防、治療或輔助治療作用的益生菌，該菌株經(jīng)本文鑒定為芽孢桿菌屬的解淀粉芽孢桿菌(Bacillus amyloliquefaciens)。本研究以群體感應(yīng)理論為指導(dǎo)，提取H24的天然發(fā)酵產(chǎn)物，分別以體外(in vitro)、體內(nèi)(in vivo)方式研究該天然菌株對腸出血性大腸桿菌O157∶H7菌Sakai株的抑制作用。 體外實(shí)驗(yàn)部分包括H24的天然發(fā)酵產(chǎn)物對Sakai菌株生物膜形成的抑制作用的研究以及對Sakai菌株志賀毒素表達(dá)抑制作用的研究。其中O157生物膜的形成與志賀毒素的表達(dá)都間接受控于該病原菌的QS系統(tǒng)，并且這兩項(xiàng)指標(biāo)也是該菌致病力的重要組成部分。
[Abstract]:Enterohemorrhagic Escherichia coli (O157:H7), as a pathogen of new infectious diseases, can lead to hemorrhagic enteritis (hemorrhagic colitis,HC) and renal hemolytic uremic syndrome (hemolytic uremic syndrome,HUS), which seriously endangers human health. Antibiotics can not be used in clinical treatment of infectious diseases of Escherichia coli O157:H7. The reason is that the antibiotics used in the traditional treatment are based on the compounds isolated from the system which is closely related to the growth and division of bacterial cells. Because the screening principle of these compounds is to kill or inhibit the growth of bacterial cells, it will cause the activation of SOS system of bacterial cells, which will lead to the short-term expression of Shiga toxin Stx1 and Stx2 encoded by lytic bacteriophages 933v and 933w in O157:H7 genome, thus accelerating the death of hosts. Therefore, screening drugs and / or probiotics that do not induce Shiga toxin expression in order to prevent and control diseases caused by pathogenic bacteria such as Escherichia coli O157:H7 is of great significance in both theoretical and clinical disease prevention and control. In this paper, the feasibility of using Bacillus probiotics to control Escherichia coli O157:H7 infection was studied. Bacterial intercellular communication system, quartile induction (quorum sensing,QS) system, plays an important role in coordinating the physiological activities of pathogenic bacteria in the process of infecting the host. The system coordinates the physiological activities of the whole bacterial population by producing a class of chemical signal molecules called self-inducing substance (autoinducer,AI). The toxin release of many pathogens is regulated by QS system. Therefore, the antibacterial drug (antibacterials), screened by the QS system of E. coli O157:H7 and other pathogens may not kill bacteria directly, but only block or interfere with the communication between individuals in the population, and then prevent them from releasing toxins, which has become the latest space for drug screening in the world at present. Intestinal probiotics is another way to treat intestinal pathogenic microbial infections such as O157:H7, which has its advantages over antibiotics, including the lack of drug resistance. Moreover, the H24 strain studied in this paper is a probiotics which has universal preventive, therapeutic or auxiliary therapeutic effect on diarrhea in chickens, pigs, cattle and other animals. The strain has been identified as Bacillus amylopectin (Bacillus amyloliquefaciens). In this paper. In this study, the natural fermentation products of H24 were extracted under the guidance of quartile induction theory, and the inhibitory effect of the natural strain on enterohemorrhagic Escherichia coli O157:H7 strain Sakai was studied by (in vivo) in vitro (in vitro),. In vitro experiments included the inhibitory effect of H24 natural fermentation products on biofilm formation of Sakai strain and the inhibitory effect on the expression of Shiga toxin of Sakai strain. The formation of O157 biofilm and the expression of Shiga toxin are indirectly controlled by the QS system of the pathogen, and these two indexes are also an important part of the pathogenicity of the pathogen.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2006
【分類號】：R371

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