Table 203
the Following Data Were Obtained from a Broth Dilution

Table 20.3
The following data were obtained from a broth dilution test: $\begin{array} { | c | c | } \hline \text { Concentration of Antibiotic } \mathrm { X } & \text { Growth } \\\hline 2.0 \mu \mathrm { g } / \mathrm { ml } & \\\hline 1.0 \mu \mathrm { g } / \mathrm { ml } & \\\hline 0.5 \mu \mathrm { g } / \mathrm { ml } & \\\hline 0.25 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.125 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0 & + \\\hline\end{array}$ Bacteria from the 0.25 µg/ml tube were transferred to new growth media containing antibiotic X with the following results: $\begin{array} { | c | l | } \hline \text { Concentration of Antibiotic X } & \text { Growth } \\\hline 2.0 \mu \mathrm { g } / \mathrm { ml } & \\\hline 1.0 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.5 \mu \mathrm { g } / \mathrm { ml } & + \\\hline 0.25 \mu \mathrm { g } / \mathrm { ml } & + \\\hline\end{array}$
-The data in Table 20.3 show that these bacteria

A) developed resistance to antibiotics.
B) are pathogenic.
C) were killed by 0.5 µg/ml of antibiotic X.
D) were killed by 0.125 µg/ml of antibiotic X.
E) were resistant to 1.0 µg/ml at the start of the experiment.