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目的基于全基因组序列,对2株食源性产CTX-M-55型超广谱β-内酰胺酶(ESBLs)大肠埃希菌的耐药和毒力分子机制进行研究。方法采用微量肉汤稀释法对大肠埃希菌食品分离株进行药敏试验,设计产ESBLs基因引物并通过聚合酶链式反应(PCR)扩增筛选出2株产CTX-M-55型ESBLs大肠埃希菌(编号为EC001和EC002)进行全基因组测序,并进行序列型(ST)、质粒复制子类型、血清型、耐药基因和毒力因子识别。结果 2株大肠埃希菌均为头孢类和喹诺酮类抗生素双重耐药ESBLs菌株;全基因组序列分析结果显示,2株菌的血清型均为肠道致病性大肠埃希菌(EPEC)O119∶H8,ST型分别为ST21(EC001)和ST342(EC002),EC001菌株含有Inc FII、IncX1、IncY、Col156和IncI2 5个不相容群质粒,EC002菌株含有IncFII和IncX1 2个不相容群质粒,2株菌株染色体中均携带bla_(CTX-M-55)和bla_(TEM-141)2种ESBLs基因。此外,EC001菌株还携带sul2/3、tet(A)/(B)、dfrA12、strA/B、aph(3’)-IIa、cml/cmlA1、floR和oqxA/B耐药相关基因,其染色体喹诺酮耐药决定区gyr A基因存在2个突变位点(S83L,D87H)、parC基因存在1个突变位点(S80I),多粘菌素耐药相关基因pmr E基因存在3个突变位点(D73Y,M185T,S225T);而EC002菌株携带fosA和qnrS1耐药相关基因。2株菌均携带致黏附与脱落(A/E)损伤的肠细胞脱落位点(LEE)毒力岛基因esc、esp、eae A和tir,且EC001菌株还携带增强菌株在血清中存活能力的iss基因。结论对2株食源性产CTX-M-55型ESBLs大肠埃希菌进行全基因组测序以及耐药和毒力的分子机制的研究,其结果可为后续开展大肠埃希菌耐药和毒力表型预测、指导食用畜禽养殖过程中抗生素合理使用及耐药菌株防控提供依据。
OBJECTIVE: To study the molecular mechanisms of drug resistance and virulence of two ESBLs-producing Escherichia coli strains producing CTX-M-55 based on the genome-wide sequence. Methods The antibiotic susceptibility test of Escherichia coli foodstuffs was carried out by micro broth dilution method. ESBLs gene primers were designed and two strains of ESBLs producing Escherichia coli CTX-M-55 were screened by polymerase chain reaction (PCR) The whole genome was sequenced and sequenced (ST), plasmid replicon types, serotypes, drug resistance genes and virulence factors were identified. Results The two strains of Escherichia coli were double-drug-resistant ESBLs strains of cephalosporins and quinolones antibiotics. The genome-wide sequence analysis showed that the serogroups of the two strains were all pathogenic Escherichia coli (EPEC) O119: H8 and ST types ST21 (EC001) and ST342 (EC002) respectively. The EC001 strain contains 5 incompatible group plasmids of Inc FII, IncX1, IncY, Col156 and IncI2, and EC002 strain contains 2 incompatible group plasmids of IncFII and IncX1 Two strains of ESBLs genes bla_ (CTX-M-55) and bla_ (TEM-141) were carried in the two strains. In addition, the EC001 strain also carries sul2 / 3, tet (A) / (B), dfrA12, strA / B, aph (3 ’) - IIa, cml / cmlA1, floR and oqxA / There are two mutation sites (S83L, D87H) in gyr A gene, one mutation site in parC gene (S80I), and three mutations in pmr E gene of multi-drug resistant gene (D73Y , M185T, S225T), while EC002 strain carries fosA and qnrS1 resistance related genes. The two strains all carried escorting sites of estrogen island genes esc, esp, eae A and tir in the sites of adhesion and shedding (A / E) injury and the EC001 strain also carried the enhanced ability of the strains to survive in the serum iss gene. Conclusion The genome-wide sequencing of two ESBLs-producing ESBLs producing Escherichia coli strains producing CTX-M-55 and the molecular mechanism of drug resistance and virulence of CTX-M-55 ESBLs-producing Escherichia coli were studied. The results could be followed by E. coli resistance and virulence Phenotype prediction, guide the rational use of antibiotics in the process of edible livestock and poultry breeding and provide basis for the prevention and control of drug-resistant strains.