临床分离志贺菌中质粒介导磷霉素耐药基因的检测

目的在磷霉素耐药志贺菌中检测质粒介导的磷霉素耐药基因fosA、fosA3和fosC2,并分析其传播方式。方法
　　琼脂倍比稀释法测定志贺菌对抗菌药物的最低抑菌浓度(MIC)。在磷霉素耐药菌株中利用聚合酶链式反应(PCR)检测其质粒介导的磷霉素耐药基因fosA、fosA3和fosC2。对阳性扩增产物进行测序分析并对阳性菌株进行接合试验,采用琼脂倍比稀释法测定接合子对12种抗菌药物的MIC值, PCR法检测接合子质粒介导磷霉素耐药基因,肠杆菌科基因间的重复序列PCR( ERIC-PCR)法对阳性菌株进行同源性分析。结果263株志贺菌中磷霉素耐药25株、中介7株,耐药率为9．5%。 PCR结果显示18株磷霉素耐药志贺菌fosA3阳性(基因登录号为KJ716852),阳性率为6.8%,未检出fo-sA和fosC2。18株fosA3阳性株中,13株结合成功,与受体菌相比,结合子对磷霉素的MIC值明显提高, ERIC-PCR法证实部分fosA3阳性志贺菌具有同源性。结论首次在临床分离的志贺菌中检测到质粒介导的磷霉素耐药基因fosA3,虽然目前检出率不高,但其传播可造成磷霉素耐药性的扩散,需要加强监测。

Detection plasmid-mediated fosfomycin resistance genes in clinical isolated shigella

Objective To investigate plasmid-mediated fosfomycin resistance genes fosA,fosA3 and fosC2 in fosfo-mycin resistance shigella and analyze its mode of transmission. Methods Antimicrobial susceptibility testing was performed by agar dilution method. Using polymerase chain reaction( PCR) to detect the plasmid-mediated fosfomy-cin resistance genes fosA,fosA3 and fosC2 in fosfomycin resistance strains. DNA sequencing of gene-positive strains were analyzed and the conjugation experiment was performed. The minimal inhibitory concentration ( MIC) of recip-ient strains and transconjugants were tested by agar dilution method for fosfomycin and other antimicrobial agents. Plasmid-mediated fosfomycin resistance genes in transconjugants were determined by PCR,enterobacterial intergenic consensus PCR( ERIC-PCR) was employed to understand the molecular homology of the fosA3-positive isolates. Re-sults In 263 strains of shigella ,resistanc to fosfomycin was 25, intermediate resistance to fosfomycin was 7,resist-ant rate was 9. 5%. PCR results showed that 18 drug-resistant strains fosA3 positive( GenBank accession numbers of fosA3 is KJ716852), positive rate was 6. 8%, no fosA and fosC2 gene was detected. The conjugation experiments were successfully carried out in 13 PCR-positive isolates. The MIC of transconjugants against fosfomycin increased differently compared to recipient strains. The homology of partly fosA3-positive isolates was comfirmed by ERIC-PCR. Conclusion The plasmid-mediated fosfomycin resistance gene fosA3 is first detected in clinical isolates of shigella , although the plasmid-mediated fosfomycin resistance genes are lowly prevalent in clinical isolates of shigel-la,but these resistance genes can lead to the characteristic fosfomycin resistence transfer ,which indicates that more attention should be paid to this phenomenon.