结核分枝杆菌对氨基水杨酸耐药性新机理研究

发布时间：2018-01-14 09:10

本文关键词：结核分枝杆菌对氨基水杨酸耐药性新机理研究　出处：《华中农业大学》2014年博士论文　论文类型：学位论文

【摘要】：结核病是由结核分枝杆菌感染而引起的传染性疾病,时至今日仍然严重威胁着人类的健康。自从1969年利福平被发现之后就没有1个新药被应用于临床,并伴随着结核分枝杆菌耐药菌株的出现和大规模的蔓延,导致人们在选择治疗结核病的药物时受到极大的限制,所以使得人类在结核病的防控上面临着巨大的挑战。重新评估在过去几十年里我们所使用的临床药物就显得尤为重要。现有药物的作用机理和耐药机理的阐述对于结核病的防控非常关键。对氨基水杨酸(PAS),是一种临床上用于治疗多重耐药结核病(MDR-TB)的药物,它的耐药性机理至今尚未被完全阐述。PAS作为叶酸前体对氨基苯甲酸(PABA)的结构类似物,在细菌体内可以被二氢喋酸合成酶(DHPS,FolPl)和二氢叶酸合成酶(DHFS,FolC)“活化”,进而抑制二氢叶酸还原酶(DHFR, DfrA)的活性,从而阻断以叶酸为辅酶的代谢通路。所以,FolC蛋白的突变会影响PAS在细菌体内的代谢,从而导致结核分枝杆菌H37Rv的PAS耐药。在我们研究中发现,FolC底物H2Pte的结合“口袋”的氨基酸残基发生突变可以导致实验室分离的结核分枝杆菌H37Ra和牛分枝杆菌的PAS耐药菌株产生耐药性。同时我们在临床分离的85株MDR菌株中,发现有5株PAS耐药菌株同样在FolC的底物结合“口袋”的氨基酸残基发生了突变。 FolC的突变虽然会导致二氢叶酸合成酶活性的降低,但也同样会导致PAS无法在细菌体内被“活化”,从而阻断其掺入叶酸代谢。耐药突变体可以通过导入野生型的folC把其对PAS的敏感性恢复到野生型水平。PAS耐药新机理的阐述,不仅有利于建立临床耐药菌株分子诊断方法,而且有助于们进一步阐述PAS的作用机理。
[Abstract]:Tuberculosis is a contagious disease caused by Mycobacterium tuberculosis infection, today is still a serious threat to human health. Since 1969 after the discovery of rifampicin without 1 drugs were used in clinical, and accompanied by the emergence of drug-resistant strains of Mycobacterium tuberculosis and large-scale spread, cause people have been restricted in the choice of the drug treatment of tuberculosis, so that mankind is facing enormous challenges in TB prevention and control. To re evaluate the clinical drugs that we use in the past few decades is particularly important. The mechanism and the mechanism of the resistance of existing drugs is crucial for TB prevention and control.
Aminosalicylic acid (PAS), is a clinically for the treatment of multidrug-resistant tuberculosis (MDR-TB) drug resistance mechanism, it has not yet been fully described.PAS as a precursor of p-aminobenzoic acid folic acid (PABA) structural analogs of bacteria can be two dihydropteroate synthase (DHPS, FolPl) and dihydrofolate synthase (DHFS, FolC) "activation", thereby inhibiting dihydrofolate reductase (DHFR, DfrA) activity, thereby blocking with folic acid metabolic pathway of coenzyme. Therefore, mutant FolC protein affects PAS in bacterial metabolism, resulting in PAS resistant Mycobacterium tuberculosis H37Rv.
In our study, the amino acid residues with FolC substrate H2Pte pocket mutations can lead to drug-resistant strains of PAS isolated from H37Ra of Mycobacterium tuberculosis and Mycobacterium bovis resistance. At the same time we in 85 MDR strains from clinical isolates, 5 strains of PAS resistant strains found also on FolC substrate combined with the amino acid residues pocket mutations.
Although the FolC mutation may lead to a decrease of dihydrofolate synthase activity, but also lead to PAS cannot be activated in bacteria, thereby blocking the incorporation of folate metabolism. Drug resistant mutants by wild-type folC to restore the sensitivity of PAS to the new mechanism of the level of the wild type.PAS resistant paper, not only to establish the clinical drug resistant strains of molecular diagnostic methods, but also help to further elaborate the mechanism of PAS.

【学位授予单位】：华中农业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：R52

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