Effect of Erythromycin on Chronic Respiratory Infection Caused byPseudomonas aeruginosawith Biofilm Formation in an Experimental Murine Model

ABSTRACTDiffuse panbronchiolitis (DPB) is a chronic lower respiratory tract infection commonly associated with persistent late-stagePseudomonas aeruginosainfection. However, low-dose long-term therapy with certain macrolides is effective in most patients with DPB. The present study was designed to examine the effects of long-term erythromycin (ERY) therapy by using our established murine model of chronic respiratoryP. aeruginosainfection. ERY or saline was administered from day 80 after intubation with aP. aeruginosa-precoated tube for the subsequent 10, 20, 40, and 80 days. Bacteriologic and histologic analyses of the murine lungs and electron microscopy of the intubated tube were performed. In the murine model, treatment with ERY for 80 days significantly reduced the number of viableP. aeruginosaorganisms in the lungs (P< 0.05). The biofilm formed in situ byP. aeruginosaon the inner wall of the inoculation tube placed into the murine bronchus became significantly thinner after 80 days of ERY treatment. We conclude that the clinical efficacy of macrolides in DPB may be due at least in part to the reduction inP. aeruginosabiofilm formation.