The invention provides compound and salts of Formula I and II, disclosed herein, which includes compounds of Formula A and Formula B: Such compounds possess useful antimicrobial activity. The variables R2, R3, R5, R6, R7, and R9 shown in Formula A and B are defined herein. Certain compounds of Formula I and Formula II disclosed herein are potent and/or selective inhibitors of bacterial DNA synthesis and bacterial replication. The invention also provides antimicrobial compositions, including pharmaceutical compositions, containing one or more compounds of Formula I or Formula II and one or more carriers, excipients, or diluents. Such compositions may contain a compound of Formula I or Formula II as the only active agent or may contain a combination of a compound of Formula I or Formula II and one or more other active agents. The invention also provides methods for treating microbial infections in animals.