胃腔定植菌在机械通气相关性肺炎发病机制中的作用

The impact of gastric colonization on the pathogenesis of ventilator-associated pneumonia

目的 探讨胃腔内病原菌定植的影响因素以及胃腔定植菌在机械通气相关性肺炎(VAP)内源性发病机制中的作用。方法 前瞻性队列研究 ,动态观察和比较重症监护病房 (ICU)建立人工气道包括气管插管或气管切开患者 (98例 ,VAP组 5 2例 ,无VAP组 4 6例 )胃腔和口咽部病原菌定植种类、浓度、与采样时间的关系 ,以及发生肺炎后下呼吸道标本中出现病原菌的种类与时序。结果 (1)胃腔内定植菌检出率随胃液pH值升高逐渐增加。胃液pH >4时 ,胃腔内革兰阴性杆菌分离率明显上升 ,VAP组革兰阴性杆菌检出率达 5 2 5 %。胃液pH值与胃内革兰阴性杆菌浓度的对数呈正相关 (r =0 4 87,P =0 0 0 1)。胃液pH >4时的VAP发生率高于pH≤ 4 (P =0 0 17)。 (2 )VAP组肠杆菌科细菌检出率随插管时间延长而增加 ,至插管第 5天达 4 5 2 % ,无VAP组为 11 1% (P <0 0 1)。 (3)肠杆菌科细菌在胃腔和口咽部定植有先后次序 ,胃腔肠杆菌科细菌早于口咽部定植 1～ 2d ,比较肠杆菌科细菌在两部位定植次序差异有显著性 (P =0 0 15 )。 (4) 5 2例VAP患者有 12例下呼吸道病原菌呈现胃腔→口咽部→下呼吸道的逆向定植次序。 3例出现胃腔→下呼吸道的定植次序。结论 (1)胃液pH值是影响胃腔定植菌特别是革兰阴性杆菌定植的主要因素。 (2 )

Objective To investigate the risk factors for gastric bacterial colonization and its role in the endogenous pathogenesis of ventilator-associated pneumonia (VAP). Methods The type and concentration of gastric colonized bacteria and its relationship with the time when samples were collected, and with the type and occurrence order of the pathogens detected in samples from lower respiratory tract after the onset of VAP were analyzed dynamically in the patients with tracheal-intubation or tracheotomy in intensive care unit (ICU). Results (1)The isolation rate of colonized bacteria in gastric cavity was associated with the pH of gastric juice. When the pH of gastric juice was >4, the isolation rate of Gram-negative bacilli (GNB) in gastric cavity markedly increased, achieving 52.5% in VAP group, and the incidence of VAP was higher ( P =0.017). The pH value of gastric juice was positively correlated with the logarithmic concentration of GNB in gastric cavity ( P =0.001).(2) As the duration of intubation prolonged, the isolation rate of enterobacteriaceae in VAP group increased, which was 45.2% on the fifth day of intubation. In contrast, the isolation rate in non-VAP group was 11.1% ( P <0.01). (3) The colonization of enterobacteriaceae in gastric cavity was 1-2 days earlier than that in oropharynx. The order was statistically significant ( P =0.015).(4) The reverse order of stomach-pharynx-lower respiratory tract colonization was found in 12 cases of the total 52 VAP patients and the order of stomach to lower respiratory tract colonization was found in 3 cases. Conclusions (1) The pH value of gastric juice proved to be the major factor which influenced the colonization of bacteria especially GNB in gastric cavity. (2) The gastric cavity was probably a colonization place of GNB especially enterobacteriaceae. (3) The enterobateriaceae in gastric cavity tended to colonize reversely to oropharynx. (4)The phenotypic analysis of the pathogens showed that the reverse stomach-pharynx-lower respiratory tract infection route existed in VAP patients.