Experimental pneumonia with Pseudomonas aeruginosa in immunosuppressed guinea pigs as a model for biofilm-associated infection
Abstract
To establish a model where the role of bacterial biofilms in chronic pneumonia with Pseudomonas aeruginosa could be investigated, hydrocortisone-treated guinea pigs were given P. aeruginosa, strain 2126 by inhalation which were used throughout this study, in planktonic form. In these animals, the bacteria were recovered only from the lungs more than 4 weeks after infection. The persistence in bacterial colonization in the lungs coincided with the formation of glanulomatous lesions that surrounded spherical grains consisting of outer shell and inner bacterial colonies. The outer shell of grain was stained with ruthenium red and was presumed to be polyanionic and therefore to be a biofilm-like material. In normal animals without hydrocortisone-treatment, the number of neutrophils recovered from bronchoalveolar lavage fluid increased significantly from 3 hours after infection and subsequently the inhaled bacteria were eliminated from the lungs by day 3 of infection. This early influx of neutrophils into the lungs tended to be suppressed by treatment with hydrocortisone. The formation of grains did not take place in the lungs of normal animals, indicating the significant role of grain-formation in the initiation and the prolongation of bacterial colonization in the lungs. P. aeruginosa, strain 2126, incubated in saline formed thick biofilms on the surface of teflon piece. Levofloxacin (LVFX), a quinolone antibacterial, exhibited killing activity against the bacteria in in…
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