The following data were obtained from a microtiter dilution…

The following data were obtained from a microtiter dilution test. Bacteria were initially grown in the presence of different concentrations of antibiotic X, then a sample of that culture was transferred to non-selective media (a subculture) to test for growth. (+ = growth, –  = no growth) Using the table below, it can be said that antibiotic X is ________at 30 μg/ml and _______ at 60 μg/ml.   Concentration of Antibiotic X Growth Growth in Subculture       15 μg/ml + + 30 μg/ml – + 60 μg/ml – – 120 μg/ml – –