Bacterial biofilms and catheters in experimental urinary tract infection

Employing in vitro and in vivo models of catheter-associated infection, biofilm formation of Pseudomonas aeruginosa in artificial urine and bactericidal activity of several classes alone or in combination with a macrolide antibiotic were investigated. In the course of continuous urine flow, bacteria adherent to a Teflon catheter formed microcolonies at 6 h and a biofilm at 24 h. Following 24 h of urine flow, the thickness and the density of the biofilm increased to about 20 microm and 10(8) cfu/mm3, respectively. Of the antibiotics examined, the fluoroquinolones showed the most potent bactericidal activity against the P. aeruginosa biofilms. However, those antibiotics were not always potentiated by the combination with a macrolide antibiotic.