Bacterial DNase activity, treatment of the biofilm with DNase I and eDNA assay. Top: DNase activity was detected in culture supernatants of 16 ST1 isolates by measuring the halo size (cm) produced on Difco™ DNase Test Agar (BD). BU: Biofilm values for 16 ST1 isolates using inert polystyrene. Left bottom: For 16 ST1 isolates, 56U/well of DNase I were added to the culture media and the amount of biofilm accumulated determined. Right bottom: The concentration of eDNA determined in the biofilm supernatant. Isolate 08–008 (strong biofilm producer, agr-dysfunctional), 96/05 (moderate biofilm producer, agr-functional).