推荐回答（5个）
耐药性又称抗药性，系指微生物、寄生虫以及肿瘤细胞对于治疗药物的耐受性。耐药性一旦产生，药物的作用就明显下降。自20世纪40年代第一个抗生素——青霉素应用于临床上以来，目前全世界发现和半合成得到的抗生素有上万种，兽医临床上常用的抗生素有近百种，这些抗生素的长期应用，对于感染性疾病的治疗取得了很好的效果，但也使某些细菌产生了耐药性，并且不断出现新的耐药菌株。如绿脓杆菌对青霉素和其他天然抗生素具有高度耐药性。细菌耐药性的出现在兽医临床上是一个极大的问题，它可以使许多常用抗菌药物的疗效降低或失效，造成治疗上的极度困难。细菌对药物产生适应或基因发生突变的结果，使细菌产生耐药性。产生的耐药性一方面通过遗传基因可传给子代，另一方面可传给敏感菌，使敏感菌不断成为耐药菌株。所以，在兽医临床上应用抗生素时，必须严格掌握抗生素的适应证，避免滥用，防止耐药菌引起的交叉感染，能用一种抗生素控制的感染不采用多种联合应用，可用窄谱抗生素的，则不用广谱抗生素。
耐药性(Drugresistance)，又称抗药性，是指病原体及肿瘤细胞等对化学治疗药物敏感性降低。当药物不能杀死或抑制病原时，抗药性一词等于药物剂量失败或药物耐受。亦指因长期服药，造成相同剂量却不如当初有效的情况。为了保持抗生素的有效性，应重视其合理使用。
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扩展资料：
耐药性的机理
产生灭活酶
灭活酶有两种，一是水解酶，如β-内酰胺酶可水解青霉素或头孢菌素。该酶可由染色体或质粒介导，某些酶的产生为体质性（组构酶）；某些则可经诱导产生（诱导酶）。二是钝化酶又称合成酶，可催化某些基团结合到抗生素的OH基或NH2基上，使抗生素失活。
多数对氨基甙类抗生素耐药的革兰阴性杆菌能产生质粒介导的钝化酶，如乙酰转移酶作用于NH2基上，磷酸转移酶及核苷转移酶作用于OH基上。上述酶位于胞浆膜外间隙，氨基甙类被上述酶钝化后，不易与细菌体内的核蛋白体结合，从而引起耐药性。
改变细菌胞浆膜通透性
细菌可通过各种途径使抗菌药物不易进入菌体，如革兰阴性杆菌的细胞外膜对青霉素G等有天然屏障作用；绿脓杆菌和其他革兰阴性杆菌细胞壁水孔，或外膜非特异性通道功能改变，引起细菌对一些广谱青霉素类、头孢菌素类包括某些第三代头孢菌素的耐药。
细菌对四环素耐药主要由于所带的耐药质粒可诱导产生三种新的蛋白，阻塞了细胞壁水孔，使药物无法进入；革兰阴性杆菌对氨基甙类耐药除前述产生钝化酶外，也可由于细胞壁水孔改变，使药物不易渗透至细菌体内。
参考资料：
/www.sogou.com/link?url=hedJjaC291NcbygW_W8Ib2XH0kc1pIdiCgsUfxbmNplYVIK4tNlddme1HRJA7j9Ju_GLXKtxwm7RCAobxOFNUw.."target="_blank"title="耐药性_百度百科">耐药性_百度百科
细菌通过基因变异等方式产生对抗菌药物的抗药性。通俗的讲，某个抗菌药物在使用初期疗效还可以，但一段时间过后发现疗效下降，其原因可能是细菌对该药物产生的耐药性。一般可以通过病原学检查和药敏试验来确认，耐药性具体产生机制就不说了，反正是太多了。
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