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四、磺胺药和其他人工合成抗菌药 (一) 磺胺药和甲氧苄氨嘧啶目前常用的磺胺药有磺胺嘧啶(SD)和磺胺甲基异恶唑(SMZ即新诺明),它们常与甲氧苄氨嘧啶(TMP即磺胺增效剂)合用。它们的抗菌机理是:多种细菌不能利用宿主的叶酸,需利用对氨基苯甲酸(PABA)、二氢喋啶和谷氨酸在二氢叶酸合成酶的作用下,合成二氢叶酸。二氢叶酸在还原酶作用下,还原成四氢叶酸,四氢叶酸参与细菌的核酸代谢。磺胺类药与PABA相似,因此防碍了二氢叶酸的合成。TMP则抑制二氢叶酸还原酶,影响四氢叶酸的合成。因此磺胺和TMP在不同环节干扰细菌的核酸代谢,起到很强的抑菌甚至杀菌作用。人体二氢叶酸还原酶对TMP敏感性差
Sulfa drugs and other synthetic antibacterial drugs (A) sulfa drugs and trimethoprim Currently commonly used sulfa drugs are sulfadiazine (SD) and sulfamethoxazole (SMZ or cotrimoxazole), they often Trimethoprim (TMP sulfonamide synergist) combined. Their antibacterial mechanism is: a variety of bacteria can not take advantage of the host folic acid, the need to use p-aminobenzoic acid (PABA), dihydropteridine and glutamate in the dihydrofolate synthase role, the synthesis of dihydrofolic acid. Dihydrofolate reductase role, reduced to tetrahydrofolate, tetrahydrofolate involved in bacterial nucleic acid metabolism. Sulfonamides are similar to PABA and therefore prevent the synthesis of dihydrofolic acid. TMP inhibits dihydrofolate reductase, affecting the synthesis of tetrahydrofolate. Therefore, sulfonamides and TMP interfere with the nucleic acid metabolism of bacteria in different aspects, play a strong antibacterial or bactericidal effect. Human dihydrofolate reductase is less sensitive to TMP