院内肺炎逆行感染途径的Southern印迹杂交分析

目的　为确证胃→咽→下呼吸道逆行感染途径存在与否 ,研究胃液 pH值变化与医院感染性肺炎 (NP)发生的关系。方法　以气管切开 (或插管 )患者为研究对象 ,用防污染标本刷 (PSB)采集标本 ,由细菌表型分型 ,直至质粒DNA、酶切、Southern印迹杂交等基因分型 ,前瞻性观察NP的发生情况。结果　 11名患者有逆行感染存在 (发生率 2 2 %) ,应用质粒图谱、酶切图谱和Southern印迹杂交等分子生物学技术进行同源性分析 ,证明其有很高的同源性。结论　存在胃→咽→下呼吸道逆行感染途径 ,NP的发生与胃液 pH值显著相关。

Retrograde Transmission for Nosocomial Pneumonia: A Southern Blotting Analysis

OBJECTIVE To explore the evidence of the retrograde transmission route from stomach to oropharynx to lower respiratory tract of the bacteria causing nosocomial pneumonia and investigate the relationship between the incidence of nosocomial pneumonia and the pH value of stomach. METHODS The study was conducted in patients requiring mechanical ventilation or tracheostomy in departments of neurology and neurosurgery of three teaching hospitals. The secretion of lower respiratory tract was collected by protected specimen brush(PSB) and the specimens were cultured quantitatively. At the same time, the bacterial samples of gastric aspirates were cultured and the pH value of gastric aspirates was determined using a digital acid-base analyzer. All patients were monitored for the development of nosocomial pneumonia every 2 days. The gene typing of the bacteria in the same phenotype from lower respiratory tract secretion and gastric aspirates was taken by plasmid profile analysis, restriction endonuclease fingerprint analysis and Southern blotting analysis.RESULTS In 11(22%) cases of nosocomial pneumonia, the identical organisms were isolated first from the gastric samples. They were homologous, showing the same pattern in plasmid profile, restriction endonuclease fingerprint and Southern blotting analysis. CONCLUSIONS The retrograde route of transmission is confirmed to be existed the risk factor in nosocomial pneumonia.The occurrence of nosocomial pneumonia is significantly associated with the increasing in gastric pH.