Resistance to Antibiotics in Plankton and Biofilm Cultures of Pseudomonas aeruginosa Clinical Strains.

Biofilms formed by Pseudomonas aeruginosa strains isolated from biomaterial of patients with implant-associated infection are characterized by much higher resistance to antibiotics of various classes than plankton cultures of these strains. The concentrations of antibiotics causing the death of 90% of P. aeruginosa biofilm (MIC90) was 2-6 μg/ml for fluoroquinolones, 267-356 μg/ml for cephalosporins, and 92-215 μg/ml for amikacin, which significantly (p<0.05) differed from MIC90 for plankton cultures that did not exceed 0.8 μg/ml for fluoroquinolones, 19 μg/ml for cephalosporins, and 3 μg/ml for amikacin. The degree of the microbial biofilm maturity also affected antibiotic resistance.