Experimental study on retrograde route of transmission of nosocomial pneumonia

  Objective   To study the retrograde route of transmission from stomach to oropharynx to lower respiratory tract and observe the relationship between the incidence of nosocomial pneumonia and the pH value of stomch.

  Methods   The study was conducted in patients in requiring mechanical ventilation or tracheostomy, the secretion of lower respiratory tract was collected by protected specimen brush(PSB).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 randomly amplified polymorphism DNA(RAPD)in the same phenotype bacteria.All patients were monitored for development of nosocomial pneumonia.

  Results   In 11(22%)case of nosocomial pneumonia, the identical or ganisms were isolated first in the gastric samples and then one to two days later in tracheal secretion.They were very homologous, exhibiting the same fingerprinting in plasmid profile, endonuclease fingerprint and RAPD.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   The retrograde route of transmission was confirmed to be existed and it was one of the risk factors in nosocomial pneumonia.The occurrence of nosocomial pneumonia was significantly associated with the rise of gastric pH.