亚剂量抗生素诱导抗性基因水平迁移

Antibiotics Induce Horizontal Gene Transfer of Resistance at Sublethal Concentrations

为探究亚剂量抗生素诱导下编码广谱β-内酰胺酶(extended-spectrumβ-lactamase,ESBL)基因的接合转移(conjugation),使用从新加坡主要医院的废水中直接分离的可合成ESBL的铜绿假单胞菌(P.aeruginosa)和大肠杆菌(E.coli)菌株作为ESBL编码质粒的供体,以携带绿色荧光蛋白(green fluorescent protein,GFP)基因的耐氯霉素(chloramphenicol,CHL)大肠杆菌SCC1(E.coli SCC1)作为受体,借助响应面分析,检测并分析了携带有ESBL编码基因的质粒在亚剂量水平的四环素(tetracycline,TC),磺胺甲噁唑(sulfamethoxazole,SMZ)和头孢他啶(ceftazidime,CAZ)单一暴露和共同暴露时,从供体菌株接合传递至受体菌株的特征.结果发现,ESBL编码质粒可在无诱导抗生素胁迫下,以平均0.0015和0.0042的频率分别由铜绿假单胞菌和大肠杆菌供体接合转移至受体大肠杆菌SCC1菌株,具有较低的"适应性代价",并在质量浓度低于最小抑菌浓度(minimum inhibitory concentration,MIC)的抗生素暴露下更易在大肠杆菌菌株之间传递.大肠杆菌菌株之间的接合转移显著发生在质量浓度低于0.03 mg·L-1的TC与质量浓度低于0.002 mg·L-1的CAZ单一暴露或共同暴露时,并可被亚MIC的TC显著抑制.铜绿假单胞菌与大肠杆菌间的接合转移可在5倍MIC的TC、CAZ共同暴露时被显著诱导,未检测到亚MIC水平抗生素对其的促进作用.

In order to explore the conjugation of genes encoding extended-spectrumβ-lactamase(ESBL),ESBL-expressing P.aeruginosa and E.coli strains isolated from the wastewater of major hospitals in Singapore were used as donors.gfp-tagged E.coli SCC1 strains resistant to chloramphenicol(CHL)were chosen as recipients.Using response surface analysis,we detected and analyzed the induction of conjugal transfer under single-exposure and co-exposure of tetracycline(TC),sulfamethoxazole(SMZ),and ceftazidime(CAZ)at sublethal concentrations.It was found that the ESBL plasmid could be conjugal transferred from P.aeruginosa and E.coli strains to the recipient E.coli SCC1 strains at an average frequency of 0.0015 and 0.0042,respectively,without stress from inducing antibiotics,thus showing a low fitness cost and higher conjugal frequency between E.coli strains under the exposure of sub-MIC antibiotics.A significant conjugation between E.coli strains occurred under the single-exposure or co-exposure of a TC concentration of<0.03 mg·L-1 and a CAZ concentration of<0.002 mg·L-1,as inhibited by a sub-MIC level of TC.The conjugation between P.aeruginosa and E.coli strains was stimulated under the exposure of TC and CAZ with concentrations 5-times larger than the MIC,while no significant induction was detected from the sub-MIC antibiotics.