通气机相关肺炎的分子流行病学研究

A molecular and epidemiology study in patients with ventilator associated pneumonia

目的从分子水平确定通气机相关（ＶＡ）肺炎细菌来源及种类。方法用保护性标本刷（ＰＳＢ）采集机械通气（ＭＶ）患者下呼吸道分泌物，同时从其它部位（如病房空气，患者胃、咽及呼吸器湿化瓶等）采样，定量培养，并以ＰＳＢ采样培养结果纯菌浓度≥１０３ｃｆｕ／ｍｌ和医院肺炎诊断标准作为确定ＶＡ肺炎诊断依据。对分离之菌株应用细菌质粒和染色体ＤＮＡ酶切图谱分析，对６５例ＭＶ患者进行微生物监测。结果１９例发生革兰阴性（Ｇ－）杆菌肺炎，病原菌主要为胃逆行定殖，即由胃到咽，然后定殖于气管支气管树；２０例发生革兰阳性（Ｇ＋）球菌肺炎，病原菌主要来自空气直接在下呼吸道定殖。结论（１）ＶＡ肺炎中Ｇ＋球菌者占相当比例；（２）Ｇ－杆菌和Ｇ＋球菌所致感染途径可能不同。

Objective To evaluate causative agents in patients with ventilatorassociated (VA) pneumonia epidemiologically, then to provide useful suggestion for diagnosis and treatment of VA pneumonia. Method Prospectively, a protected specimens brush was used to obtain the secretion of lower respiratory tract of 65 patients, who had been receiving mechanical ventilation or tracheostomy for more than 72 hours. At the same time, other samples were collected from the relevant places, including pharyngeal and gastric juice of patients as well as other persons, ward′s air. The secretion obtained were cultured with a quantitative method. Then all bacteria isolated were studied with the analysis of pattern of plasmids and chromosomal restriction endonuclease. Result It was showed that the route of infection of the Gram negative bacilli in VA pneumonia (19 cases) was intrinsic, a retrograde colonization from patient′s stomach, that was the pattern of clonization from stomach to pharynx, then into lower respiratory tract, and the Gram positive staphylococcus spread mainly through the ward′s air, then directly into lower respiratory tract, or extrinsic (20 cases). Conclusion The Gram positive staphylococcus is also major disease producing germs in VA pneumonia, and the infection routes of G + and G - bacteria might be different.