The "Mutant Prevention
Concentration" *
"When Mycobacterium bovis BCG and Staphylococcus
aureus were plated on agar
containing increasing concentrations of fluoroquinolone, colony numbers exhibited a sharp drop, followed by a
plateau and a second sharp
drop.
The
plateau region correlated,vith the presence of first-step resistant mutants. Mutants were not recovered at concentrations
above those required for the
second sharp drop, thereby defining a mutant prevention concentration (MPC).
A C8-methoxy group lowered the MPC for an N-1-cyclopropyl fluoroquinolone"