【作者】 易秀丽；

【导师】 黄一帆；

【作者基本信息】 福建农林大学 ， 基础兽医学， 2008， 硕士

【摘要】 畜牧水产上抗生素类药物大量而频繁的使用导致的细菌耐药性问题己引起国内外广泛关注。为了解水环境中细菌对常用抗生素的耐药情况以及残留兽药进入水环境中对水源细菌耐药性的影响,本试验以粪肠球菌为指示菌,对不同水环境中细菌耐药性进行了监测,同时建立模型池塘生态系统研究不同用药方式对水源细菌耐药性的影响。试验分为两个部分:(一)从天然水源(福州国家森林公园和模型池塘生态系统)、水产养殖场(鱼塘、鳗鱼场、牛场鱼塘和猪场鱼塘)、人类居住环境(生活小区、污水沟及闽江)和水生动物(蝌蚪、鳗鱼、黄颡鱼、鲮鱼和鲫鱼)共分离出539株粪肠球菌,根据美国临床和实验室标准协会(CLSI)推荐的微量肉汤稀释法进行药敏试验,了解水源粪肠球菌对6种常见抗生素的耐药情况。结果如下:不同水源分离粪肠球菌对6种常见抗生素的耐药情况不同:天然水源分离菌耐药率、耐药水平、多重耐药率和耐药指数(ARI)在本试验中最低;其次为生活小区池塘和鳗鱼场,除对土霉素的耐药率较高,分别为69.2%和100%外,对其他抗生素耐药率均比较低。水产养殖场(鳗鱼场除外)、人类居住环境(污水沟和闽江)和水生动物耐药情况较复杂,不仅耐药率、耐药水平和ARI较高,多重耐药情况也比较严重。同时,水生动物分离菌耐药情况比相应水环境严重。试验结果证明了细菌耐药性与水源受抗生素污染之间存在一定的联系。水环境中抗生素暴露水平越高,分离菌耐药率、耐药水平和多重耐药现象越严重;反之,耐药情况越简单。(二)通过建立模型池塘生态系统,选取土霉素和环丙沙星来研究抗生素以不同的途径进入水环境后对水源细菌耐药性的影响。试验采用直接用药组、含药饲料组和含药粪便组3种不同的用药方式,于投药前和投药后不同时间点采样进行细菌药敏试验,结果如下:3种用药方式下,含药饲料组对水源粪肠球菌耐药性影响最大。在投药后3d,分离菌耐药率达到最高,同时土霉素饲料组和环丙沙星饲料组出现了MIC值大于256μg/mL的高水平耐药菌,所占比率分别为63.3%和20%;之后耐药率回落比较缓慢,4个月后,仍有20%以上的耐药菌。直接用药组对水源细菌耐药性的影响略大于含药粪便组。用药后含药粪便组细菌耐药率降低最快,2个月后几乎无耐药性。土霉素药物组与环丙沙星药物组相比,分离菌耐药情况更严重,用药4个月后,3种方式下仍然可以分离出比对照组比例高的土霉素耐药菌。试验结果提示用药方式不同,细菌耐药率、耐药水平也不一样;此研究结果可为水产养殖如何正确用药提供科学依据。更多还原

【Abstract】 With the abuse of antibiotics in animal husbandry and aquaculture, the problem of antibiotic resistance of bacteria has caused wide attention at home and abroad. To study the resistance of bacteria to common antibiotics in aquatic environment and the influence of veterinary drug residues on water source bacteria. Enterococcus faecalis was chosen as indicative bacteria in this study, bacterial resistance in different aquatic environments was monitored. Then, model pond ecosystem was built to research the effect of different medication ways on antibiotics resistance of water source Enterococcus faecalis. This study includes two parts.(1) 539 strains of E. faecalis were isolated from natural water (national forest park in fuzhou city and model pond ecosystem), aquaculture farms (fish farm, eel farm, cattle-fish farm and pig-fish farm), human inhabitation environments (residence district pond, sewage and Minjiang River), and aquatic animals (tadpoles, eel, yellow catfish, mud carp and crucian carp), antibiotic susceptibility test was carried by micro-broth-dilution method according to Clinical and Laboratory Standards Institute (CLSI).The objective was to investigate antibiotic resistance conditions to six kinds of antibiotics of water source E. faecalis. The result indicated that:Different water source E. faecalis had different resistance conditions. Natural water isolated E. faecalis had the lowest resistance rate, resistance level, multi-drug resistance rate and antibacterial resistance index(ARI). Residence district pond and eel farm isolated E. faecalis had high resistance rates to oxytetracycline, which were 69.2% and 100%, respectively; and had low resistance rates to other antibiotics. Aquaculture farms (except for eel farm), human inhabitation environments (sewage and Minjiang River) and aquatic animal isolated E. faecalis showed complex resistance conditions, they had not only high resistance rates, resistance levels and ARI, but also severe multi-drug resistance conditions. At the same time, aquatic animal isolated E. faecalis had more serious resistance than relevant aquatic environments isolated E. faecalis.The results proved that there was a definite relation between bacterial resistance and water pollution conditions by antibiotics. The higher the antibiotics exposure level was, the heavier the resistance rate, resistance level and multi-drug resistance of E. faecalis were; conversely, the resistance conditions of isolates were simple.(2) By building model pond ecosystem, we chosen two antibiotics (oxytetracycline and ciprofloxacin) to study the effect factors of resistance of water source E. faecalis. Three different medication groups including direct medication group, drug-containing feed group and drug-containing feces group were used, samples were collected before medication and after medication in different time points, then antibiotic susceptibility test was carried. The result indicated that:Comparison the three medication ways, drug-containing feed group showed the most influence to antibiotic resistance of water source E. faecalis. On the 3rd day after medication, the resistance rates of isolates reached to the highest, and there were some high level drug-resistant bacteria with MIC≥256μg/mL in oxytetracycline-containing feed group and ciprofloxacin-containing feed group, the rates of them were 63.3% and 20%, respectively; then the resistance rate fell slowly. After 4 months, resistant bacteria still could be isolated; the rate was above 20%. The influence of water source E. faecalis in direct medication group was a little bigger than drug-containing feces group. But resistance rate in drug-containing feces group fell fast; and became few after 2 months. Compared with ciprofloxacin-containing group, E. faecalis isolated in oxytetracycline-containing group showed the severer resistance conditions. After 4 months, we could still isolate E. faecalis resistant to oxytetracycline.The results suggested that different medication ways had different resistance rates and resistance levels. It also provided reliable medication evidences for aquaculture farming.更多还原