饲用抗生素的作用机制及其危害

饲用抗生素的作用机制及其危害 一、饲用抗生素的作用机制 自从1946年Moore等发现链生素在肉鸡饲料中具有促生长作用以后，抗生素就开始作为饲料添加剂，广泛应用于饲料中，针对抗生素促生长机制的研究也随之深入。目前尽管抗生素的促生长效果得到一致证实，然而它们提高动物生长的机制还比较模糊。 1、营养生理学机制 抗生素可通过抑制环境中的抗生长因子产生的亚临床症状而促进动物生长，部分抗生素可以使蛋白质代谢相应得到改善，佟建明(2001)发现在肉鸡日粮中添加金霉素，可降低血液中氨、尿酸含量，增加氮沉积。抗生素还具有降低肠壁厚度、改善肠粘膜结构、降低肠道维持需要的作用，从而有利于营养物质的吸收。 2、微生物学机制 饲用抗生素能够减轻肠道微生物与宿主营养竞争，有人推测，抗生素抑制了小肠内的微生物生长和活性，减少了微生物对能量和养分的吸收利用，从而增加了宿主的可利用养分。饲用抗生素还可以降低动物组织及血液和环境中氨的浓度。因此，细菌产生的有毒代谢产物的减少可能是抗生素促生长作用的一种机制。抗生素的另一个重要机制是抑制了肠道内微生物胆酸的生物转化，而胆酸浓度降低，平均日增重和饲料效率相应提高。 rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities 3、免疫学机制 事实证明抗生素不仅抑制机体免疫系统的发育，而且还抑制机体的免疫反应。Gordon(1995)试验发现，饲喂抗生素的常规鸡，其小肠黏膜内淋巴细胞滤泡和游离浆细胞数目显著降低，接近无菌鸡。Naqi(1984)和Cook(1984)研究发现，抗生素处理可降低鸡消化道淋巴组织(包括法氏囊、盲肠扁桃体、肠道固有膜)中产免疫球蛋白的细胞的生成和分布密度，显著降低血清IgM浓度。Rijkers等(1980，1981)发现饲喂土霉素可引起鲤鱼体液免疫抑制，降低血清中免疫球蛋白含量，并使脾脏、前胃和后胃内噬斑形成细胞的形成率降低80,。Voiculesu等(1983a，1983b)的研究表明，红霉素、粘杆菌素可显著抑制机体的体液和细胞免疫。 佟建明(2001)、张日俊(2000)在对金霉素影响肉仔鸡免疫机能的研究中发现，日粮中添加金霉素不但对肉仔鸡的胸腺、脾脏和法氏囊的发育指数具有显著的降低作用，还降低肉仔鸡的T、B淋巴细胞转化率和有丝分裂活性，使体液免疫和细胞免疫功能降低，从而得出了金霉素对免疫系统具有屏障作用，并借此促进肉鸡生长的结论。Klasing等(1987，1988)就机体免疫系统与动物生长之间的关系作了详细的综述，认为抗生素整体上是通过直接(直接影响免疫系统的反应能力)或间接(通过降低微生物侵袭强度)影响免疫系统，防止免疫系统激活，从而促进动物生长。 rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities 迄今为止，虽然人们对饲用抗生素的促生长机制提出了多种假设和推论，并取得了许多科学依据，但一些试验结果存在很大的分歧，抗生素促生长的确切机制仍然没有被完全阐明。 二、滥用抗生素形势严峻 半个多世纪来，抗生素给养殖业创造了巨大的经济效益。抗生素一直作为饲料促生长添加剂被广泛应用，然而由于抗生素在畜禽饲料中的广泛应用尤其是超标使用，引起各种病原微生物产生抗药性，以及动物的二重感染，严重影响畜禽健康状况;还被怀疑会引起畜禽产品中药物残留，不仅影响畜禽产品的质量及其安全性，还会导致人类体内病原微生物对抗生素产生耐药性，进而直接威胁人类健康。近二三十年来，抗药菌株的比率不断增加，人类医治细菌传染性疾病的难度越来越大，所需抗生素的有效使用剂量节节攀升，人们开始相信是动物产品药物残留引起，因而对饲用抗生素的反对意见日趋强烈。 中国是抗生素使用大国，也是抗生素生产大国。人均年消费量138克左右(美国仅13克)。我国抗生素一半用于临床，一半用于畜牧养殖业。专家推算，中国每年生产的大约21万吨抗生素原料中有9.7万吨用于畜牧养殖业，占年总产量的46.1%。世界上没有哪个国家如此大规模地使用抗生素，欧美等发达国家对抗生素的监管非常严格和到位，购买抗生素需要专业医生开具的处方。这些情况表明中国成为了世界上滥用抗生素问题最严重的国家之一。 全行业在追求最大经济利益的驱动之下惘顾社会责任和rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities 食品安全，在饲料中随意添加或超量添加抗生素，可以说从动物出生到屠宰上市整个生产周期中无时无刻不存在抗生素的滥用。抗生素的滥用造成了严重的公共卫生问题。 1、细菌抗药性越来越普遍，越来越严重 畜牧业中，大肠杆菌、葡萄球菌、沙门氏菌等过去并不严重或较少发生的细菌病，现已上升为家禽的主要传染病之一，这与长期滥用抗生素有直接关系。从1990年至2011年先后有数十位学者对中国的猪源大肠杆菌和禽源大肠杆菌进行耐药性测定，结果显示:大肠杆菌的耐药性越来越强，近几年来95%的抗生素已经失去敏感性，菌株平均携带的耐药基因多达17种。抗生素应用越严重的地区，细菌的耐药性就越强，在这些抗生素污染严重的地区寻找敏感药物变得越来越困难。一旦爆发耐药性细菌病，就会造成严重的经济损失。开发一种新的抗生素一般需要10年左右的时间，而一代耐药菌的产生只要很短的时间。显然，抗生素的研制速度远远赶不上耐药菌的繁殖速度，用抗菌素治病救人的美景将会消失。 虽然耐药性因子的传递频率只有10-6，但由于细菌数量大、繁殖快，在这一频率下，仍造成抗药菌株的扩散、蔓延，而且可以使一种细胞产生多种耐药性。抗生素滥用导致耐药菌株增加，而抗生素饲料添加剂长期、大量不合理使用是其中一条主要原因。由此可见，抗生素对畜禽肠道微生物的污染和人类对自然环境的破坏同样可怕，需要相当长的修复时间。更可怕的是自然界rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities 的破坏极易引起人们的关注，而滥用抗生素对畜禽肠道微生态系统的破坏却长期被人们所忽视。 2010年8月初以来,印度、巴基斯坦、加拿大、比利时、英国和日本等国家先后报道出现了超级细菌(NDM-1)感染者,全球至少有170人被感染,并造成多起病人死亡事故。2010年10月26日中国疾病预防控制中心通报三起感染超级耐药致病细菌病例，其中死亡1例。2011年在中国杭州，研究超级细菌的专家在重症监护室的病人身上也发现了金黄葡萄球菌的“超级细菌”MRSA细菌。大量耐药菌的出现对医疗及社会造成的危害巨大，可能会造成抗感染治疗的失败，住院时间的延长，甚至患者的死亡。上世纪60年代，全世界每年死于感染性疾病的人数约为700万，而这一数字到了本世纪初上升到2000万。死于败血症的人数上升了89%，大部分人死于超级病菌带来的用药困难。 2、长期使用抗生素造成畜禽机体的免疫力下降 饲用抗生素的作用机理之一就是通过抑制动物的免疫反应达到促生长的目的。Naqi(1984)和Cook(1984)研究发现，饲用抗生素可降低鸡消化道淋巴组织(包括法氏囊、盲肠扁桃体、肠道固有膜)中产免疫球蛋白的细胞的生成和分布密度，显著降低血清IgM浓度。Rijkers等(1980，1981)发现饲喂土霉素可引起鲤鱼体液免疫抑制，降低血清中免疫球蛋白含量，并使脾脏、前胃和后胃内噬斑形成细胞的形成率降低80,。Voiculesu等(1983a，1983b)的研究表明，红霉素、粘杆菌素可显著抑制机rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities 体的体液和细胞免疫。 大量抗生素在其被摄入机体后，会随血液循环分布到淋巴结、肾、肝等各组织器官，动物机体的免疫能力就会被削弱。抗生素还会导致抗原质量下降，直接影响免疫过程，从而对疫苗的接种产生不良影响。磺胺类药物在动物幼体期使用会抑制骨髓的造血功能，引起粒细胞减少、溶血性贫血、再生障碍性贫血等情况发生。氯霉素作用于胸腺，可使其皮质、髓质界限失常;作用于脾脏，可使其滤泡消失、白髓结构松散;作用于盲肠扁桃体，可使其淋巴组织减少，还可损伤肝组织和肾组织，破坏骨髓造血功能，全面破坏免疫应答，使动物抵抗力、免疫力严重下降。 3、长期用抗生素可引起畜禽内源性感染和二重感染 抗生素虽有自己的抗菌谱，但它作用于病原菌的同时也会影响体内有益菌群生长，特别是长期大量使用，使机体内菌群失调，微生态平衡破坏，潜伏在体内的有害菌趁机大量繁殖，从而引起内源感染。二重感染也是由于施用大量抗生素杀灭某种细菌时，破坏微生态平衡，另外一种或多种内源或外源病菌随即再次感染机体造成的(薛恒平，1998)。 4、长期使用抗生素会在畜产品和环境中造成残留 药物残留是饲料中添加抗生素争议之一。 随意添加或超量添加饲用抗生素，会使肉、蛋和奶等农畜产品中蓄积抗生素,通过食物链进入人体内，使人们天天间接接触抗生素，导致人体患病时用抗生素治疗的效果消失。此外药物都有副作用，没有一种rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities 抗菌药物绝对安全，仅程度不同而已。如磺胺类药物易使人产生过敏和变态反应;氯霉素引起再生性、障碍性和溶血性贫血，血小板减少和肝损伤;四环素类有光敏性和胃肠道反应;喹乙醇是基因诱变剂;呋喃唑酮诱发动物癌变等(曾书琴，2004)。虽然某些药物已禁用，但有些仍在使用。 抗生素被吸收到体内后，分布于全身。抗生素在体内器官中以肝脏分布较多，而在肌肉和脂肪中分布较少。抗生素的代谢途径多种多样，但大多以肝脏代谢为主。一些性质稳定的抗生素被排泄到环境中仍能稳定地存在一段时间，从而造成环境中的药物残留，这些残存的药物，通过畜产品和环境慢慢蓄积于人体和其它植物体中，最终以各种途径汇集于人体，导致人体产生大量耐药菌株，失去对某些疾病的抵抗力，或因大量蓄积而对机体产生毒害作用。 另外，抗生素还有致基因突变、引发畸形和诱发癌症等毒副作用。据《北京日报》报道，我国7岁以下儿童因为不合理使用抗生素造成耳聋的数量多达30万，占总体聋哑儿童的30%-40%，而一些发达国家只有0.9%。在住院的感染病患者中，耐药菌感染的病死率为11.7%，普通感染的病死率只有5.4%。 rAt present, we have formed a "three-three" Park. …… Industrial Park, according to ... ... The instructions of comrade, focus on development needs in the next decade, based on the original, and then extended the 6 square kilometers. Of the Park, to further improve the roads, power supply, communications, water supply and drainage and sewage pipe network and other infrastructure, to achieve full coverage of infrastructure and interconnection with the facilities and raise capacity. Each park to determine 1 leading industries, in particular stone Materials, cans, gloves, through guided, force and other measures to promote the "road company" Park, industrial agglomeration. Currently, to focus on building better ... ... Industrial Park, ... ... Wood Park as the starting area of the industrial park, planners need to take out plan, start construction as soon as possible, undertake in a timely manner ... ... Transfer of the wood industry. This opportunity slip by, so the timing must be tight. Second is to optimize government service. Low efficiency of government services, departments do not coordinate the views of businesses large, poor business environment, it is ... ... Short Board, decide to change. We will continue to deepen reform of the administrative examination and approval system, good digestion, implement the Government canceled, adjustment and devolution of administrative examination and approval matters, strengthen the existing supervision in matters of administrative power, has made it clear to cancel, are not allowed to keep or disguised approval. To do list list of administrative powers and responsibilities