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目的对血流感染患者临床分离的利奈唑胺中介粪肠球菌的毒力因子及耐药机制进行初步研究。方法从2例血流感染患者血标本中分离2株利奈唑胺中介粪肠球菌,分析患者治疗经过,2株分离菌编号为A、B,测定其对利奈唑胺和万古霉素的最低抑菌浓度(MIC),采用聚合酶链反应(PCR)扩增毒力基因(esp、asa1、gelE、ace、agg、efaA、cylA、hyl)和利奈唑胺耐药相关基因,包括23SrRNA V区基因、cfr、cfr(B)及optrA基因片段,其中23SrRNA V区基因扩增产物送测序并分析有无突变位点。结果 2例患者培养出利奈唑胺中介粪肠球菌后均使用利奈唑胺治疗控制了临床症状。菌株A、B对万古霉素、替考拉宁、氨苄西林、呋喃妥因敏感,对利奈唑胺中介(MIC均为4μg/mL),对万古霉素敏感(MIC分别为1μg/mL和4μg/mL)。2株菌均含有多种毒力因子,菌株A仅cylA、hyl为阴性,菌株B仅hyl、esp为阴性,其余毒力基因均为阳性。菌株A的23SrRNA V区存在G2621T突变,菌株B未发现突变位点。菌株A和B耐药基因cfr、cfr(B)、optrA均为阴性。结论此研究中血流感染患者分离的利奈唑胺中介粪肠球菌对万古霉素和氨苄西林敏感,虽治疗结果提示利奈唑胺仍有效,但临床中选用利奈唑胺治疗需谨慎。靶位突变是该类药物重要的耐药机制,临床中治疗该类药物不敏感粪肠球菌感染需足够重视,其治疗策略仍需进一步探讨。
Objective To study the virulence factors and drug resistance mechanisms of Enterococcus faecalis isolates clinically isolated from patients with bloodstream infections. Methods Two strains of Enterococcus faecalis isolated from lineal blood in 2 patients with bloodstream infection were analyzed. After treatment, the two isolates were identified as A and B, and the minimum inhibitory concentrations of linezolid and vancomycin were determined. (MIC). Virulence genes (esp, asa1, gelE, ace, agg, efaA, cylA, hyl) and linezolid resistance genes were amplified by polymerase chain reaction (PCR) , Cfr, cfr (B) and optrA gene fragments, 23SrRNA V region gene amplification products sent sequencing and analysis of the presence or absence of mutation sites. Results Linezolid was used to control the clinical symptoms in 2 patients after the linezolid was injected into midazolam. Strains A and B were sensitive to vancomycin, teicoplanin, ampicillin and nitrofurantoin, both to linezolid (MICs were 4μg / mL) and to vancomycin (MICs were 1μg / mL and 4μg / mL respectively ). The two strains contained a variety of virulence factors. The strains A only cylA, hyl negative, strain B only hyl, esp negative, the rest virulence genes are positive. There was a G2621T mutation in the 23SrRNA V region of strain A and no mutation site in strain B. Strain A and B resistance gene cfr, cfr (B), optrA were negative. Conclusion In this study, linezolid was isolated from patients with bloodstream infection and was sensitive to vancomycin and ampicillin. Although the treatment results suggested that linezolid remained effective, the treatment with linezolid was clinically precautionary. Target mutation is an important drug resistance mechanism of these drugs, the clinical treatment of such drugs is not sensitive to Enterococcus faecalis infection should pay enough attention to its treatment strategy still needs further study.