呼吸机相关性肺炎患者下呼吸道标本检出的粘质沙雷菌β-内酰胺酶检测及同源性分析

Analysis of the β-lactamases and homology of Serratia marcescens from lower respiratory tract samples in Ventilator-associated pneumonia

目的研究呼吸机相关性肺炎患者检出的粘质沙雷菌药物敏感性、β-内酰胺酶基因型和同源性。方法针对我院重症监护病房明确诊断为呼吸机相关性肺炎患者,于2015年3月1日至2017年3月1日,连续收集下呼吸道标本分离的粘质沙雷菌,使用全自动细菌鉴定和药敏分析仪PhoenixTM-100鉴定细菌种类,并测定其最小抑菌浓度,并用E-TEST试纸条方法验证;PCR方法测定TEM、SHV、CTX-M、CMY、FOX、OXA、MOX、DHA、CMY1-23、ACT-1和MIR等β-内酰胺酶基因型;脉冲场凝胶电泳分析菌株的同源性。结果共收集粘质沙雷菌67株,亚胺培南与美罗培南的敏感率均为100%,其次哌拉西林/他唑巴坦、头孢西丁、阿莫西林/克拉维酸、头孢他啶、阿米卡星的敏感率分别为97.59%、96.18%、93.27%、85.07%、82.13%,但对呋喃妥因、复方新诺明、氨苄西林、环丙沙星等敏感率均低于50%;10株头孢他啶和头孢噻肟耐药的粘质沙雷菌超广谱β-内酰胺酶均为阳性,PCR实验证明,几乎都产CTX-M-14型超广谱β-内酰胺酶和CMY-1头孢菌素酶。脉冲场凝胶电泳的结果证明,有两组具有同源性的细菌。结论我院呼吸机相关性肺炎患者检出的粘质沙雷菌对碳青霉烯类抗生素全敏感,但部分菌株可通过携带CTX-M型超广谱β内酰胺酶或/和CMY-1型头孢菌素酶导致对头孢他啶和头孢噻肟耐药,并存在多个克隆株的传播,因此,针对呼吸机相关性肺炎患者,急需做好院内感染的防控工作。

Objective To analysis theβ-lactamases and homology of Serratia marcescens isolates from lower respiratory tract samples in Ventilator-associated pneumonia.Methods Aimming at the patients suffering from ventilator-associated pneumonia(VAP)from intensive care unit,we collected Serratia marcescens isolates continuously from mar 1st 2015 to mar 1st 2017.The identification and the minimum inhibitory concentration(MICs)were performed by using PhoenixTM-100,and the MIC were validated by E-TEST method finally.The beta-lactamases genotype of TEM,SHV,CTX-M,CMY,FOX,OXA,MOX,DHA,CMY1-23,ACT-1 and MIR were performed by PCR.Pulsed-field gel electrophoresis(PFGE)was performed to analyze the homology of those isolates.Results A total of 67 Serratia marcescens isolates were collected,which were all sensitive to imipenem and meropenem.The sensitive rates to piperacillin/tazobactam,cefoxitin,amoxicillin/clavulanic acid,ceftazidime,amikacin were 98.59%,97.18%,94.37%,88.73%,85.92%,respectively.However,the susceptibility rates to furofloxacin,compound sulfamethoxazole,ampicillin,ciprofloxacin were all less than 50%.Ten isolates of Serratia marcescens were all resisitant to ceftazidime and cefotaxime,and almost all the isolates produced CTX-M-14 extended spectrum beta-Lactamases and CMY-1 AmpC beta-Lactamases.Of particular note was that two groups were clonal relationships.Conclusions Some Serratia marcescens isolates from lower respiratory tract samples in our hospital were resistant to ceftazidime and cefotaxime by encoding CTX-M-type ESBLs and/or CMY-1-type AmpC beta-lactamases.The results suggested that there exists cloning spread between different strains.So it is very important to to prevent and control the multidrug-resistant bacteria in our hospital.