Figure 2.

Concentration-dependent killing of biofilm-grown clinical P. aeruginosa isolate cells exhibiting different resistance levels. Minimum concentrations of killing (MCK) for tobramycin (A), ciprofloxacin (B) and colistin (C) that are required to reduce biofilm-grown cells by 99.99 % (4-log reduction of CFU; MCK99.99) are depicted in box-plots for clinical isolates, which were categorized into sub-groups exhibiting the same MIC values (x-axis). Boxplot elements are: center line – median; box limits – upper and lower quartiles; whiskers – minimum and maximum. Each dot represents one clinical isolate. S, susceptible; I, intermediate; R, resistant. Strains were categorized according to breakpoints defined by CLSI guidelines.