Retrograde spread of organisms from ventilator to patient via the expiratory limb.
D003428:Cross Infection / Q000209:etiology*; D046508:Culture Techniques; D005374:Filtration / Q000295:instrumentation; D006801:Humans; D006813:Humidity; D007239:Infections / Q000382:microbiology; D008722:Methods; D008962:Models, Theoretical; D011550:Pseudomonas aeruginosa / Q000254:growth & development*; D012705:Serratia / Q000254:growth & development*; D013997:Time Factors; D012122:Ventilators, Mechanical