Genome macrorestrictionª²pulsed field gel electrophoresis in the study of retrograde route of transmission for nosocomial pneumonia

    DAI Qian, DENG Hong, ZHOU Yong, NING Tao, LI Jianª²Feng

    1Department of Military Hygiene, 2Department of Urology Surgery, Affiliated Hospital, Jilin Military Medical College, Fourth Military Medical University, Jilin 132013, China

    ¡¾Abstract¡¿ AIM£º To explore the evidence of retrograde route of transmission from stomach to oropharynx to lower respiratory tract and investigate the relationship between the incidence of nosocomial pneumonia and the pH value of stomch. METHODS£º The study was conducted in patients in department of neurology and neural surgery of three teaching hospitals requiring mechanical ventilation or tracheostomy,the secretion of lower respiratory tract was collected by protected specimen brush (PSB) and the specimens were carried out for quantitative culture of bacteria. At the same time, the bacterial samples of gastric aspirates were collected to culture and the pH value of gastric aspirates was determined using a digital acidª²base analyzer. All patients were monitored for development of nosocomial pneumonia every two days. The gene typings of the bacterial from lower respiratory tract secretion and gastric aspirates were taken by plasmial profile analysis,restriction andonuclease fingerprint analysis and Genome Macrorestrictionª²Pulsed Field Gel Electrophoresis (GMª²PFGE) in the same phenotype bacteria. RESULTS£º In 11(22%) case of nosocomial pneumonia, the identical organisms were isolated first in the gastric samples and then one to two days later in tracheal secretion. They were very homologous,exhibiting the same fingerpriting in plasmid profile, endonuclease fingerprint and GMª²PFGE. Two days after being perfused into the stomach through masogastric tubes, Methylene blue was found in the secretion of throat and lower respiratory tract. The bacterial counts in gastric aspirates increased significantly with gastric pH. CONCLUSION£º The retrograde route of transmission is confirmed to be existed and it is one of the risk factors in nosocomial pneumonia.The occurrence of nosocomial pneumonia is significantly associated with the rising of gastric pH. ......