Effect of Tobramycin on the Biofilm-Forming Forms of Pseudomonas aeruginosa Isolates Isolated from Patients with Cystic Fibrosis.

The biological properties of nine clinical isolates of Pseudomonas aeruginosa obtained from five patients with cystic fibrosis were assessed. Six different sequence types of P. aeruginosa with different biofilm-forming abilities were detected. It was found that at the initial stage of adhesion, four isolates were tobramycin-resistant, while in the formed biofilm, almost 100% survival was recorded. The properties of the isolates were associated with the sequence type: when it changed, the biofilm-forming ability decreased, but the number of viable cells resistant to tobramycin at a concentration of 2 μg/ml increased. The study shows that the existence of a biofilm is a key factor ensuring, despite constant antimicrobial therapy, the long-term persistence of P. aeruginosa in patients with cystic fibrosis.