Towards individualized diagnostics of biofilm-associated infections: a case study

Determination of the biofilm-active score (BAS) of the three antibiotics on P. aeruginosa biofilm-grown bacteria. An exemplary data set on the responsiveness of biofilm-grown bacteria of the clinical isolate Iso1525 towards various concentrations of the antibiotics aztreonam (AZT), colistin (COL), and tobramycin (TOB) is shown. We used the untreated control to set the corresponding green biovolume values as the 100% vitality value. The green biovolume can increase to values larger than 100%, if biofilm formation is induced by non-lethal antibiotic concentrations (a common observation). The isolate Iso1525 is non-responsive towards the activity of AZT and TOB, but concentrations ≥16？μg？ml？1 COL lead to a reduction in the green biovolume by >75%. This corresponds to a BAS of +++. The BAS is dependent on the green biovolume reduction and the minimal antibiotic concentration necessary to reach the reduction. For details of BAS categorizations see Table S