撤除教槽料抗生素和无机铜对哺乳仔猪粪便大肠杆菌耐药性的影响

Effects of withdrawing antibiotic and copper in creep feed on the resistance of Escherichia coli isolated from feces of sucking piglets

[目的]本试验拟通过比较采食商品教槽料(含抗生素和无机铜)和自配教槽料(不添加抗生素和无机铜)苏淮哺乳仔猪粪便中氨苄西林(AMP)、四环素(TET)、头孢噻肟(CTX)耐受肠杆菌数的差异和分离自CTX-Mac平板大肠杆菌耐药性的变化,剖析和探讨撤除饲料中的抗生素和无机铜对缓解猪源大肠杆菌耐药问题的可行性与意义。[方法]选用9窝27头7日龄哺乳仔猪,随机分为3组,每组3窝9头仔猪,从14日龄开始W0组饲喂商品教槽料,W1和W2组饲喂不同的自配教槽料,30日龄断奶,采集每头仔猪7日龄和30日龄的粪样,进行Mac平板和TET、AMP、CTX-Mac平板计数,并用琼脂稀释法检测分离自CTX-Mac平板大肠杆菌的多种抗生素和铜MIC值。[结果]7日龄时,各组仔猪粪样的肠杆菌数以及AMP、TET、CTX耐受肠杆菌数均无显著差异;30日龄时,W1组的AMP耐受、W2组TET耐受肠杆菌数显著低于W0组(P<0.05),W1和W2组CTX耐受肠杆菌数及其比例均极显著低于W0组(P<0.01)。除1株外所有的大肠杆菌均对TET和AMP耐药,约45%的大肠杆菌耐受氟苯尼考(FLO),约15%的大肠杆菌耐受环丙沙星(CIP),并不受教槽料中抗生素和无机铜撤除与否的影响。大肠杆菌对庆大霉素(GEN)和萘啶酸(NAL)的敏感性表现出一定程度的此消彼长趋势,对NAL敏感性的降低伴随着对GEN敏感性的升高。30日龄时,W0组大肠杆菌的铜抗性显著高于W1和W2组,菌株的铜抗性降低时,其GEN的耐药率显著升高(P<0.05)。[结论]撤除教槽料中的抗生素和无机铜可显著降低仔猪粪便中AMP、TET、CTX耐受肠杆菌数和比例,并显著提高大肠杆菌对铜的敏感性,但是短时间撤除抗生素和无机铜无法立刻缓解猪源大肠杆菌对TET和AMP的高耐受现象;大肠杆菌对GEN和NAL的敏感性之间、对铜和GEN的敏感性之间存在一定的此消彼长现象。

[Objectives]The aim of this paper was to evaluate the significance for withdrawal of antibiotics and inorganic copper from creep feed on controlling the drug resistance of Escherichia coli in piglets＇ gut,the number of resistant Enterobacterium recoverable from piglets＇ feces and the minimum inhibitory concentrations（ MICs） of E. coli isolated from CTX-Mac plates were compared between suckling piglets feeding commercial creep feed（ with antibiotics and inorganic copper） and self-made creep feed（ without antibiotics and inorganic copper）. [Methods]27 piglets at 7 days of age（ D7） from 9 litters were randomly assigned to either a control group（ W0） or one of two treatment groups（ W1 or W2）,the W0 group was given commercial creep feed from 14 days of age,while W1 and W2 groups was given self-made creep feed from the same day. All piglets were weaned at 30 days（ D30）. Fecal samples obtained from piglets on D7 and D30 were used for enumeration of total Enterobacterium on Mac plates and resistant Enterobacterium on tetracycline（ TET）,ampicillin（ AMP）,cefotaxime（ CTX）-Mac plates. The MICs of E. coli to 6 antibiotics and copper sulfate were determined using an agar dilution method. [Results]On D7,the number of total and resistant Enterobacterium were comparable among three groups. On D30,resistant Enterobacterium numbers to AMP in W1 group and to TET in W2 group were remarkably decreased compared with W0 group（ P〈0.05）; resistant Enterobacterium number to CTC and the ratio of CTC-resistant bacteria in W1 and W2 groups were notably reduced,respectively（ P〈0.01）. Almost all E. coli isolates were resistant to AMP and TET,and about 45% and15% E. coli were resistant to FLO and CIP,respectively,but the withdrawal of antibiotics and inorganic copper had no influence. Thedecreasing susceptibility to NAL was accompanied with the increasing susceptibility to GEN of E. coli. Besides,the level of copper resistance of E. coli isolates in W0 group was significantly higher than that in W1 and W2 group,respectively（ P〈0.05）. The ratio of GEN-resistant E. coli was notably increasing（ P 0. 05）,while the copper resistance was just reverse. [Conclusions]Withdrawal of antibiotics and inorganic copper from piglets creep feed could significantly reduce the number and ratio of resistant Enterobacterium to TET,AMP and CTX,accompany with the increasing of copper sensibility. Withdrawal of antibiotics and inorganic copper couldn＇t decrease the high resistance of E. coli to TET and AMP. Meanwhile,the increase of E. coli resistance to GEN was accompanied with the decrease of resistance to NAL,a similar tendency between GEN and copper was also observed in this study,and further research was necessary.