[The study on bacterial infection in chronic lower respiratory tract infection--from the viewpoints of acute and chronic infection].

Using mainly changes in the amount of sputum as an index of the infectious course of chronic lower respiratory tract infection associated with purulent sputum over years, the disease was divided into stable and acute exacerbated phases and a bacteriological investigation using transtracheal aspiration (TTA) conducted. TTA was performed 107 and 45 episodes during stable phases and acute exacerbated phases respectively. Monomicrobial and polymicrobial infection were detected most frequently during the stable and acute exacerbated phases respectively (p less than 0.01). During the stable phases, the single organisms detected most frequently were H. influenzae (26 episodes) and P. aeruginosa (20 episodes), while in the cases in which multiple organisms were detected during stable phases, combination including H. influenzae were most common (19 episodes). H. influenzae was the most frequently detected organism in cases showing single organisms during acute exacerbated phases (7 episodes). In the cases in which multiple organisms were detected as well, H. influenzae was the most commonly detected organism assumed to predispose to exacerbation (7 episodes), while P. aeruginosa was not found. These results suggest that in chronic lower respiratory tract infection. H. influenzae and P. aeruginosa are important as persistent infective organisms, while H. influenzae are important in acute exacerbation.