Each rowfrom1 to 3 and 5 to 7 contained a different bacterial strain and rows 4 and 8 served as negative turbidity control without bacteria. On the following day, 15 μl of iodonitrotetrazolium chloride (INT, 0.5 mg/ml in 70% ethanol) was added to each well and the microplates were again incubated at 37 °C for 60 min, and in those wells, where bacterial growth occurred, INT changed from clear to purple.