摘要
从保存的2002-2009年分离的食品动物源大肠杆菌中,挑选16株blaCTX-M-14阳性菌,用PCR方法检测超广谱β-内酰胺酶(ESBLs)编码基因、PMQR耐药基因及其他重要抗生素耐药基因(rmtB和floR);通过脉冲场凝胶电泳(PFGE)及种族进化关系分析16株细菌的亲缘关系;通过接合转移试验、复制子分型和blaCTX-M-14上下游插入元件的检测,分析产CTX-M-14大肠杆菌的传播分子机制。PCR检测结果表明,16株食品动物源产CTX-M-14大肠杆菌大多属于系统发育组A组,其次为B1和D组,没有B2组;PFGE分型结果表明,同一时间内不同动物间存在产CTX-M-14共生型大肠杆菌克隆的扩散传播,但养殖场内CTX-M-14主要是随质粒或其他元件进行水平传播;质粒复制子分型结果表明,携带blaCTX-M-14的质粒属于IncK(3/14)、IncF(5/14)、IncHI2(1/14)、IncFIB和IncF(1/14)、IncHI1和IncN(2/14)、IncI1(2/14)等,且随着时间推移,复制子的种类呈增多趋势。2002-2007年的菌株blaCTX-M基因的上下游均检测到ISEcp1和IS903;但2009年菌株除了部分在上下游都可以检测到ISEcp1和IS903外,还有的只检测到上游的ISEcp1或下游的IS903;2002-2009年的菌均未检测到ISCR1。16株产CTX-M-14大肠杆菌除了携带其他ESBLs编码基因,如blaCTX-M79和blaTEM-135外,还携带其他重要抗生素耐药基因,如oqxA、floR、aac(6′)-1b-cr及rmtB,而且2002-2009年大肠杆菌携带耐药基因的种类和数量逐年增多;接合转移试验发现,2002-2005年的菌株,blaCTX-M-14往往发生单独转移,而2009年分离菌blaCTX-M-14往往和floR或rmtB位于同一质粒上发生共同转移。这说明养殖场使用氨基糖苷类或氟苯尼考等任何一种抗生素,都可以筛选出产CTX-M-14大肠杆菌并促进其扩散,所以动物养殖过程中要慎用这些抗生素。
Sixteen CTX-M-14 producing Escherichia coli isolates from food animal recovered from 2002 to 2009 were subjected to detection of extended spectrum beta-lactamases(ESBLs) encoding genes,plasmid mediated quinolone resistance determinants,and other relevant resistant genes(rmtB and floR);strains typing using PFGE and phylogrouping;bla_CTX-M-14 plasmid replicon typing,transferring of bla_CTX-M-14 by conjugation,and detection of context of bla_CTX-M-14 gene.Majority of 16 isolates were clonally unrelated by PFGE,suggesting horizontally transfer of bla_CTX-M-14 among food animals,and corresponded to phylogenetic groups A(50%),D(21.5%) and B1(28.5%).Plasmids containing bla_CTX-M-14a were belonging to IncK(n=3),IncHI2(n=1),IncHI1 and IncN(n=2),IncFIB and IncF(n=1),IncF(n=5),or IncI1(n=1),with insertion sequence of ISEcp1 upstream bla_CTX-M-14a,and apparently increased in numbers of replicon and diversity from 2002 to 2009.The increasing dissemination of bla_CTX-M-14 among different food-producing animals is mostly mediated by IncK,IncF,IncHI2,IncI1 plasmids carried by commensal E.coli.Some of CTX-M-14-producing E.coli harbored simultaneously bla_CTX-M-79 or bla_TEM-135,as well other relevant resistant genes,such as oqxA,floR,aac(6′)-1b-cr or rmtB.Bla_CTX-M-14 could be transferred separately in isolates of 2002,while co-transferred with other relevant resistant genes on the same plasmid via conjugation or transformation,suggesting co-selection and spread of CTX-M-14 producing isolates when use of any of the relevant antibiotics in animal farms.
出处
《中国畜牧兽医》
CAS
北大核心
2012年第9期195-202,共8页
China Animal Husbandry & Veterinary Medicine
基金
国家自然科学基金--广东省自然科学基金联合基金重点项目(U1031004
U0631006)
关键词
CTX-M-14
传播分子机制
复制子分型
水平传播
CTX-M-14
molecular mechanism of transmission
replicon typing
horizontal transmission